Custom folders and files are not removed during an upgrade, only defaults. If I go into my Mac Application Support directory and look for Photoshop 2021 (for example), my custom patterns are still there, they are not erased with the default patterns. So unless you deleted the Photoshop 2021 folder they should still be there. So basically check the old folder for "My Skies". Some folders are hidden by default to protect new users. I know how to unhide them in my Mac, but if you are running Windows, other Windows users can help you there.
Another idea would to check your backup files if you use system backup software.
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