Hi @drafter2ZT9Z4. Generally speaking, part files do not contain anything that indicates if they are being referenced within any assemblies or drawings, so there is no simple way to figure out 'if' it is being used / referenced by anything else, or 'what' other things it is being used / referenced by. If you have Vault, that is one of its benefits, though. It will know what all other files it is associated with. Without Vault, we can try using the Design Assistant, but it can be really slow, if you have a large pool of files for it to search through each time. The limitation of what Inventor (by itself) can find, as far as other document that are referencing a part is within the other documents that are currently open within Inventor. If the assembly is currently open, then Inventor will know if the part (that is also open) is being referenced within it.
Wesley Crihfield
(Not an Autodesk Employee)