Function description

it's in the generate attribute operator.
The idea is that you 'regenerate' your existing attribute, so you just use your existing attribute name, but generate new content for it.
The generate attribute operator contains all the search, replace, splice, trim and other functions you will need

@kayman
thnx for your reply.  I was only referring to the function description in 'generate attribute' operator. 
 I couldn't get  the syntax of the function correctly.  can I have some help to set it right? 

Yeah, takes some getting used to.
Regular expressions are your friend here, but they can be frightening if you're not used to them.

Try something as below : 
(start a new process, copy the xml, open view -> show panel ->xml -> paste -> green tick in top corner to validate and store -> back to process window)

What is does is create a new field (but you can also overwrite your existing field), uses a regular expression to remove everything that's not a digit (using \D ) and then parses it.

Now for weeks you can safely multiply by 7, for months it's not so straightforward so I just took an average of 30.
Finally I used the aggregation operator to sum them all up.

Note that in reality you can combine all of the above in a single expression using the generate attribute, but it can become a bit unreadable then. 

<?xml version="1.0" encoding="UTF-8"?><process version="9.6.000">
  <context>
    <input/>
    <output/>
    <macros/>
  </context>
  <operator activated="true" class="process" compatibility="9.6.000" expanded="true" name="Process">
    <parameter key="logverbosity" value="init"/>
    <parameter key="random_seed" value="2001"/>
    <parameter key="send_mail" value="never"/>
    <parameter key="notification_email" value=""/>
    <parameter key="process_duration_for_mail" value="30"/>
    <parameter key="encoding" value="UTF-8"/>
    <process expanded="true">
      <operator activated="true" class="utility:create_exampleset" compatibility="9.6.000" expanded="true" height="68" name="Create ExampleSet" width="90" x="112" y="34">
        <parameter key="generator_type" value="attribute functions"/>
        <parameter key="number_of_examples" value="1"/>
        <parameter key="use_stepsize" value="false"/>
        <list key="function_descriptions">
          <parameter key="MyDays" value="&quot;3 days&quot;"/>
          <parameter key="MyWeeks" value="&quot;8 weeks&quot;"/>
          <parameter key="MyMonths" value="&quot;10 months&quot;"/>
        </list>
        <parameter key="add_id_attribute" value="false"/>
        <list key="numeric_series_configuration"/>
        <list key="date_series_configuration"/>
        <list key="date_series_configuration (interval)"/>
        <parameter key="date_format" value="yyyy-MM-dd HH:mm:ss"/>
        <parameter key="time_zone" value="SYSTEM"/>
        <parameter key="column_separator" value=","/>
        <parameter key="parse_all_as_nominal" value="false"/>
        <parameter key="decimal_point_character" value="."/>
        <parameter key="trim_attribute_names" value="true"/>
      </operator>
      <operator activated="true" class="generate_attributes" compatibility="9.6.000" expanded="true" height="82" name="Generate Attributes" width="90" x="246" y="34">
        <list key="function_descriptions">
          <parameter key="MyParsedDays" value="parse(replaceAll([MyDays],&quot;\\D&quot;,&quot;&quot;))"/>
          <parameter key="MyParsedWeeks" value="parse(replaceAll([MyWeeks],&quot;\\D&quot;,&quot;&quot;))*7"/>
          <parameter key="MyParsedMonths" value="parse(replaceAll([MyMonths],&quot;\\D&quot;,&quot;&quot;))*30"/>
        </list>
        <parameter key="keep_all" value="true"/>
      </operator>
      <operator activated="true" class="generate_aggregation" compatibility="9.6.000" expanded="true" height="82" name="Generate Aggregation" width="90" x="380" y="34">
        <parameter key="attribute_name" value="TotalDays"/>
        <parameter key="attribute_filter_type" value="subset"/>
        <parameter key="attribute" value=""/>
        <parameter key="attributes" value="MyParsedDays|MyParsedMonths|MyParsedWeeks"/>
        <parameter key="use_except_expression" value="false"/>
        <parameter key="value_type" value="attribute_value"/>
        <parameter key="use_value_type_exception" value="false"/>
        <parameter key="except_value_type" value="time"/>
        <parameter key="block_type" value="attribute_block"/>
        <parameter key="use_block_type_exception" value="false"/>
        <parameter key="except_block_type" value="value_matrix_row_start"/>
        <parameter key="invert_selection" value="false"/>
        <parameter key="include_special_attributes" value="false"/>
        <parameter key="aggregation_function" value="sum"/>
        <parameter key="concatenation_separator" value="|"/>
        <parameter key="keep_all" value="true"/>
        <parameter key="ignore_missings" value="true"/>
        <parameter key="ignore_missing_attributes" value="false"/>
      </operator>
      <connect from_op="Create ExampleSet" from_port="output" to_op="Generate Attributes" to_port="example set input"/>
      <connect from_op="Generate Attributes" from_port="example set output" to_op="Generate Aggregation" to_port="example set input"/>
      <connect from_op="Generate Aggregation" from_port="example set output" to_port="result 1"/>
      <portSpacing port="source_input 1" spacing="0"/>
      <portSpacing port="sink_result 1" spacing="0"/>
      <portSpacing port="sink_result 2" spacing="0"/>
    </process>
  </operator>
</process>

 

@kayman thanks.
this improves.  But this will work  if consider those values as three different attributes.  But all these  row values are part of single attribute "Age".  I think this will need a different function ?

@kayman, thanks.  this improves.
But this will work if we consider those values as three different attributes. 
But there, all these row values are part of single attribute 'age'.  I think this will need a 
different function?

Ah, wasn't that clear to me. In the end it means just a bit more complex find and replace logic. 

something like this : 

input 3 days ,   8 weeks ,  10 months
output = 359

<?xml version="1.0" encoding="UTF-8"?><process version="9.6.000">
  <context>
    <input/>
    <output/>
    <macros/>
  </context>
  <operator activated="true" class="process" compatibility="9.6.000" expanded="true" name="Process">
    <parameter key="logverbosity" value="init"/>
    <parameter key="random_seed" value="2001"/>
    <parameter key="send_mail" value="never"/>
    <parameter key="notification_email" value=""/>
    <parameter key="process_duration_for_mail" value="30"/>
    <parameter key="encoding" value="SYSTEM"/>
    <process expanded="true">
      <operator activated="true" class="utility:create_exampleset" compatibility="9.6.000" expanded="true" height="68" name="Create ExampleSet" width="90" x="179" y="34">
        <parameter key="generator_type" value="attribute functions"/>
        <parameter key="number_of_examples" value="1"/>
        <parameter key="use_stepsize" value="false"/>
        <list key="function_descriptions">
          <parameter key="myField" value="&quot;3 days ,   8 weeks ,  10 months&quot;"/>
        </list>
        <parameter key="add_id_attribute" value="false"/>
        <list key="numeric_series_configuration"/>
        <list key="date_series_configuration"/>
        <list key="date_series_configuration (interval)"/>
        <parameter key="date_format" value="yyyy-MM-dd HH:mm:ss"/>
        <parameter key="time_zone" value="SYSTEM"/>
        <parameter key="column_separator" value=","/>
        <parameter key="parse_all_as_nominal" value="false"/>
        <parameter key="decimal_point_character" value="."/>
        <parameter key="trim_attribute_names" value="true"/>
      </operator>
      <operator activated="true" class="generate_attributes" compatibility="9.6.000" expanded="true" height="82" name="Generate Attributes" width="90" x="313" y="34">
        <list key="function_descriptions">
          <parameter key="days" value="parse(replaceAll(myField,&quot;(\\d+) days?[ ,]+(\\d+) weeks?[ ,]+(\\d+) months?&quot;,&quot;$1&quot;))"/>
          <parameter key="days" value="days + (parse(replaceAll(myField,&quot;(\\d+) days?[ ,]+(\\d+) weeks?[ ,]+(\\d+) months?&quot;,&quot;$2&quot;))*7)"/>
          <parameter key="days" value="days + (parse(replaceAll(myField,&quot;(\\d+) days?[ ,]+(\\d+) weeks?[ ,]+(\\d+) months?&quot;,&quot;$3&quot;))*30)"/>
        </list>
        <parameter key="keep_all" value="true"/>
      </operator>
      <connect from_op="Create ExampleSet" from_port="output" to_op="Generate Attributes" to_port="example set input"/>
      <connect from_op="Generate Attributes" from_port="example set output" to_port="result 1"/>
      <portSpacing port="source_input 1" spacing="0"/>
      <portSpacing port="sink_result 1" spacing="0"/>
      <portSpacing port="sink_result 2" spacing="0"/>
    </process>
  </operator>
</process>

@kayman,  thanks for your reply.  I m sorry that I didnt make it clear to understand the data . 
All these are different rows of a single attribute.  Means  - 3 days can be one row,  8 weeks another row , 10 months
 another row.. , 6 years can be an another one.  like that  there are many rows. 
Im enclosing the sample of that attribute " Age pet".  kindly have a look on  it. 

@Thiru, Now I get it :-)

In this case use 'contains' is what you need, in combination with the if statement.