How does a vault with different folders not allow duplicate parts?

i.e.

A screw that is used on many parts will be located where?

If each "folder" holds a full assembly with all its parts, what if the parts need to be in other "folders"? How do I avoid duplicate parts?

I recently started working for a company that has had solidworks for about 10 years but have never used PDM, only folders... I'm researching ways we can start using PDM but we already have a crazy amount of duplicate parts. For example:

How should I go about cleaning this up?