In the Project Panel, you have Video Usage. Unfortunately, as one can have many Instances of a Source Clip, and those can have different In & Out Points, just pure Usage does not mean that you have used the same Clip multiple times, as each Instance can be quite different.
Now, in PrPro's (later versions), if one Rt-clicks on an Asset in the Project Panel, they can Reveal in Sequence, and see each use. I do not know if later versions of PrE have added that, or similar. And again, because a Clip (or segment of a Clip) is used multiple times, it could well be just a different Trim from the "master" Clip.
The only way that I can think of in PrE (at least up to the versions that I have installed to test) would be to step through the Timeline with PageDn, noting the file names. I would probably toggle the Clip Display to Name, and not All Frames, so as to not be distracted by the Frame Displays, and only to see the Clip Names. This will obviously be an exercise in memory.
Hopefully, later versions of PrE have added something like the Reveal in Project (PrE does not have Sequences, so only one Timeline - the Project's), and one can use that to see all Instances. You would still need to determine if those Instances contain the same Trim Points, which would mean that they WERE duplicated.
Good luck, and let's let a user with the newest version comment on Reveal in Project, or similar.
PS - In the Project Panel, one can click+drag on the Video Usage Column header/title and move it closer to the Clip Name. That might keep one from having to scroll about the Project Panel.
Thanks. I will do that. U have been a big help.
You are most welcome.
Good luck and happy editing.