All of my original media files have disappeared after I opened a library backup

I updated to the most recent version of FCPX and then had to downgrade back to the previous version because I made the mistake of not checking beforehand that certain vital plug-ins would be compatible (they weren't). Unfortunately I had already updated my library for the newer version of FCPX, so I went to my library backups and opened a recent one from just before the update. Upon doing this I found that nearly all of the clips in my library had been washed over with the red "Missing File" screen. My original media folder is now missing terabytes and terabytes of files.
PLEASE tell me these files are simply hidden somewhere else.

Where was the original media stored? Was it external media or managed inside the library bundle?

I have my library and original media stored on an external SSD

UPDATE: Thankfully I have found the original media files through "Show Package Contents" of the main library. Is there a way to immediately relink all of these to the clips in the library backup, or do I have to manually relink each one individually (there are over 500 files that need to be relinked)?

I've figured it out. Apologies for creating this thread. I was panicking