How would you import a kv6 file?

I once made a bunch of of .kv6 models and I thought it would be cool if I could make a game with them.

You need to change the kv6 to a different format. Get the trial of Paint3D(or anything else) and export as an obj, you may get different results depending on what program you use to import the kv6 and export out to a format unity supports which you can find here.