How do I undo an incorrect batch rename?

If you are on mac, buy a copy of "A Better Finder Rename" Its a utility app which will save your ass at least once a year! <https://www.publicspace.net/ABetterFinderRename/index.html>
You have no idea how useful this is!
Peter

Thank you. I’m new to Bridge/ Photoshop. I really do appreciate all suggestions/advice, especially when it has to do with anything computer related. I’m an older mom who’s just gone back to school for photography and boy things are different.
Anyway, again many many thanks

You can revert to the original file name assigned in-camera if that's what you were using. See this post:
http://asktimgrey.com/2017/07/18/revert-to-original-filename/

Lot's of tutorials on the Web covering Bridge Batch Renaming. Here's one:
https://www.youtube.com/watch?v=_X7PddkeQ74

Sort by size...you will have to distinced sizes groups the small ones are the JPGs