Only way I can think of is if you make a separate collision group for each model. I’m not sure how efficient this would be at a larger scale but it sounds like it could work.
Your question is very poorly worded (Not necessarily your fault since its hard to discuss the outcome you want when talking about collision groups) but ima have a shot of answering what I think your asking, which is how to make parts in a collision group only collide with each other and nothing else.
Two ways, both untested. Option A is preferable but may not work, Option B will definitely work but less efficient.
Set the parts to CanCollide false then add the parts to a collision group and set the collisions to true (This should in theory work but as I said untested.)
Add every part to a different collision group and set the collisions with group a to false.