Migrating music from an external driver to iTunes on Mac Book Pro (running Monterrey)

I need advice on migrating my old iTunes media from an external drive to my new Mac book pro. I have a relative large prior iTunes media folder save on my time Machine back up ext drive & on a separate ext drive. probably about 250GB or so. I have tried using Migration Assistant but it set up a new second user on the Mac Book and moved on the library data and not the media. Moreover I do not really want a second user anyway. I have deleted the new user to get back where I started. I also tried importing my old iTunes media folder on the sep ext hard drive by clicking on the "add music" option in iTunes on the Mac book. that just took several hours ands got hung up. Nothing new added. So again, at least, I am back where I started. I should say that a lot of the older media folder consists of music have digitized from vinyl and music I imported from CDs. And a lot I have prev purchased from Apple. Incidentally only a small portion of my purchases have shown up in my new iTunes app on the Mac Book. It appears to be just the most recent purchases. Finally, I should say the old iTunes was created on 2008 iMac running El Capetian. I do have or have had in the past serval iPads, iPods, iPhones, and another older Mac book pro so I am not new to Apple.