I assume you mean for Platinum Arts Sandbox?

(this is general chat for the site, not the game but it is okay). The format needs to be md2 or md3 which is quake 2 and quake 3 format. I think max might have an exporter for them. Also I think we can use quake software tools to convert files. I need to look more into it and when more info I'll be posting tutorials. Take care and thanks for your interest!
-mike