Not helpful, as the old iTunes library not exists. I already spent months last year to transfer the play counts (and playlists) to the target computer (Mac 1), that had the Music app, not iTunes. When done, the other Mac (Mac2) that had iTunes, got updated its MacOS, so that I no longer had iTunes, from that date. Mac 2 thus began with a fresh Music app and library, with no play counts, as could not find a way to transfer those items. Online help, to transfer from iTunes to Music app failed to get the playlists and play counts transferred.
Once the play counts got near enough, I did delete the iTunes library from EHD.
I repeat, playlists nowhere near as difficult as play counts. It takes a day to manually transfer playlists, but months to transfer play counts.
Now, I want to transfer the Music library on Mac 1, with the play counts and playlists intact, to external drive, due to storage running out on its internal hard drive. I'm sure there are more steps to take, than already answered. Those steps to be consolidation, and move location, As well as drag and drop. Those steps may be precise and done in the correct sequence. This is need to know. No step-by-step guide online found for this yet.
Failing the above, now thinking now to get Mac 2 running by re-installing Mac OS on an external drive, then running Migration Assistant onto that when it wakes up, and see if that works.