Please post your System Information as Lightroom Classic (LrC) reports it. In LrC click on Help, then System Info, then Copy. Paste that information into a reply. Please present all information from first line down to and including Plug-in Info. Info after Plug-in info can be cut as that is just so much dead space to us non-Techs.
Refer to the tutorial link above given by @GoldingD
But First be viewing your Library in GRID mode (either single Folder, or All Photographs) and select all photos to rotate ,
Then incur the 'Rotate' commands either from the top Menu, or from the Rotate Icons on the Toolbar [T].
Or- Keyboard shortcuts- CTRL+[ CTRL+]
The Spray Can (also on the tool bar) can also be defined to Rotate photos, and you simply 'Spray' photos to rotate them, even spraying across multiple thumbnails to rotate as you spray. (Remember to replace the spraycan on its icon when finished using!)