So I reinstalled windows 10 and decided on keeping my files and I reinstalled all my apps but I don't know how to locate my photos. It just opens Lightroom as if I've never uploaded a photo to my catalog
Sorry that Lightroom is no longer showing your images after you;ve reinstalled Windows 10 on your computer.
Which version of Lightroom are you using? Lightroom desktop or Lighroom Classic?
Reinstalling Windows 10 should also reimage all the files/folders. Lightroom catalog is saved in the Pictures folder by default. Do you have access to the original catalog or backups of your Lightroom catalog stored on an external device?
If you were using Lightroom then your photos are safely stored in the cloud. You should see them when you sign into your account. If you were using Lightroom Classic your photos were on a local hard drive, not inside of Lightroom. If you didn't understand this, and didn't pay attention to where your photos copied to when imported, they were in the Pictures folder. They may still be in the Pictures folder depending on how you reinstalled Windows.