HaloMods "Classic" Read-only Archive

Can somebody please tell me how to convert models? Because when I want to edit a halo model in gmax, I tried just putting .gmax after it instead of .obj and that did'nt work. I just installed gmax because I want to start moddeling... so this is something I really need to know.

Thank you!

i thought gmax could import .obj files. when you go to import, do you change the file format type to .obj? if not, i know that there' converters, just google it.