1) The images were moved for a reason; undoing the move is counter-productive.2) In most cases, the move was done long ago, and I no longer know the original location.
By @lowellnelson
So, undo the move, and then move them PROPERLY to wherever you want the photos to be, so Lightroom Classic doesn't lose track of them. See Part 2 — Updating Folder Location here https://www.computer-darkroom.com/lr2_find_folder/find-folder.htm (Or just use Part 1 of the document to re-connect LrC to the new location of these photos, no need to delete the photos from LrC)
2) In most cases, the move was done long ago, and I no longer know the original location.
But Lightroom Classic remembers where the photos were. That's its job, to remember these details. In the metadata panel of the Library Module, next to "Folder" is the name of the folder where LrC thinks the photos were. If you hover your mouse over the folder name, it will tell you the FULL PATH of the folder.