So I changed what you said, and nothing changed. You meant to change it after new modelresourcelocation, right?
also where do I put that other thing you were saying.
Just to clarify when I do that really long line, I do
Minecraft.getMinecraft().getRenderItem().getItemModelMesher().register(mod name.item name, 0, new ModelResourceLocation("ModID:json file", "inventory"));
this is probably wrong, sorry, I'm used to python