OBJ+MTL for mobs plz

Hi, I'm new here and I'm trying to use .OBJ + .MTL to make a custom Iron Golem, but MCreator only accepts .java for mobs, and this option only comes in BlockBench if you use the modified entity method. I would like to know if I can use OBJ for mobs, because when I use the modified entity option, I have some problems.

 Thanks <3 :)