What do your hard drives look like with their folder hierarchies?
Do you have any recent backups of your catalog with everything still OK?
(Don't try anything yet.)
FYI - There are obviously some serious weaknesses in Lightroom that might screw the existing folders when moved. After spending all day back and forth with Adobe support, I finally had to bite the bullet and reorganize my entire photo library. It amazes me that Lightroom puts users at risk of such a serious, non-reversable mistake. All from single file transfer (the way it’s recommended by Adobe themselves).
Lightroom does OK when moving a very small number of files.
However, when you are looking to move a larger number of files, or moving any number of folders, you really should be doing that at the OS level using Explorer or Finder then relocating the folders in LR.