Have your Fotos Libraries opened on a Mac with a newer system version? Then you can no longer open them with an older version of Photos.
Fotos on macOS 14 should still be able to open your iPhoto Libraries from iPhoto '09 or iPhoto '11, as well as all your Photos Libraries, unless you downgraded to an earlier system version or have touched your libraries in a newer system version. Did you downgrade from a newer system version or opened the libraries on a Mac with a newer system? Then you will need to update your Mac to the last system version you used to open your Photos Libraries. But do not upgrade to macOs Ventura, before you have migrated all iPhoto Libraries to Photos.
If you never opened your Photos Libraries in a Photos version newer than the Photos 7 on macOS 12.4, your current system, make sure, that you are opening the Photos.app installed in your Applications folder. An icon in the Dock or an alias on the Desktop may still be linked to on older version, perhaps on a backup drive.
To launch the Photos.app coming with your system version open the Applications folder, select Photos there, then hold down the options key ⌥ while launching Photos. Release the key, when the dialog to select a library appears and select the library you want to open.