I received a model as a .stp file and it has two subassemblies. I need to be able to use the model with the regular assembly features - mates, exploded view, etc.  I'm able to pack and go to save all of the parts as solidworks part files, but the subassemblies don't convert to regular assembly files. Is there a trick to unpacking an entire assembly or do I need to ask for the .stp files for the sub assemblies every time? Thank you