If you did that
removing the %LocalAppData% folder
then you have already deleted all your library data.
Unless you have previously moved your Plex data folder to a different location/drive.
If you can’t remenber whether you did that, take a look into the windows registry.
See if the registry string mentioned in this post [HowTo] Plex database modification - Moving media the right/wrong way does exist.
If it does, inspect its content. Now verify that the location therein does indeed still exist and is accessible for reading and writing (and the storage volume it’s on has still plenty of free space).
