Hi Stewartm32,
welcome to the Apple (user-to-user) Community.
Re: "My Playlists (plural) are empty.
Don't know how to repopulate original playlist content"
Wondering if the music files the playlists referred to were moved. The playlists wouldn't be able to connect with the music files. Returning the music files to the place they were originally (when the playlists were first created) may help in that situation.
Seems the only way to restore from 2 years back, would be if you had a back-up copy of the playlists, eg: stored on a different device, or external hard drive. And, if the music files are still where they were stored when the playlists were made, you may then be able to import and use the playlists.
Else if you still have all the music files, maybe create some new playlists.
All the best :-)