How to replace a time value

Hi dears
I've struggled to change a certain of time value for almost one day, which is turning the "12:00:00 AM" into "12:00:00 PM", I 've used "Date to nominal" to deal with it, but after doing so the time value would be changed, so I gave up this method.

Now I am trying to use "Generate Macro", but I have no idea how to write the function expression, could you please tell me?

Sincerely,
Starfish