Converting Proteus PCB to Altium PCB file
I suspect that those are Gerber photoplot files.

Looking at some of the types listed, I'd say cadacam-bottom-silkscreen.txt should be "Silk Bot", ...bottom_solder_resist.txt should be "Mask Bot".  Others seem pretty obvious, although you may have a bit of a problem guessing at the valid type names.

The file names seem to me to be self-explanatory, if you have some idea of the photoplot files required to make a PC board.