Lightroom Classic update 13.3

I need suggestions or help here. I just installed the update to Lightroom Classic and after opening it, it has "lost" almost all of my previously imported photos and collections I had set up in the past. I mean I have 300 photos now in my library when I used to have thousands, all split into the separate trips. I tried to reinstall the older version but the photos are still gone. This is hundreds and hundreds of hours of work lost.