Mesh import error in CADFeko

Hello everyone, I am a student and I have been using Altair feko for my project work. I am trying to import a .dat file with x,y,z coordinates in CADFeko (.dat file is mentioned as CONCEPT format in CADFeko). Bu it throws an ERROR 30573, that I need to specify whether the file is a wire file or surface file. But I don't know where and how do I specify it.  Can somebody kindly help me