CD's uploaded in iTunes don't show up in Music

I had an extensive CD library, which I decided was taking up too much room, so I uploaded ALL of them into iTunes (after YEARS of iTunes being the go-to app on Apple and other devices). Shortly after, Apple got rid of iTunes and started using "Music" instead.

While all of the songs show up on my old iMac (2015 version), none of them are available on my MacBookAir (2019 version).

When I plugged in the external HD from the iMac (which has the songs) into my MacBook, Music still won't let me import the songs.

Even when I log in with the exact same Apple ID.

(disclaimer: I don't have extra Apple Cloud storage, as I never needed it before)

Help! I donated all my CD's, but I haven't had music on my laptop or phone in forever (I sync my phone with my laptop - which has no songs currently)

How can I get all of the music I PURCHASED ON CDs (NOT in iTunes) into my Music account?