How to make a 3D particle

So basically, say I have a model I wanted to use for a particle instead of a flat particle that is buggy when I use a key bind to release it, how would I go about implementing this model to the code of the particle? Could it be a Java file (Better for me) or does it have to be a block file, e.g. OBJ file? (Not as convenient) I'm sure there's a way to do this, but I'm also sure it takes some coding. I'm fine with a little bit of coding, as long as you could please tell me where to insert the code snippet inside of the particle file? If you need, I can give you the file of the particle for some help? Thanks so much in advance, I've been trying to figure this out since day one!