Music File Management

My iTunes library is quite large and resides on an external hard drive. I have been using a MacBook Air to access the music files, but it is running Mojave and I need to keep it that way. So I upgraded an idle MacBook Pro to Catalina so I’d have all the latest macOS and Apple apps. I opened iTunes on the MacBook and found that it had about 600 songs on file, for right now all in the Cloud somewhere. (I don’t use iCloud all that much except for email, and the songs that are there are all in the files on the external drive.) I figured I could just connect the hard drive to the MacBook, repoint the source of the music in iTunes preferences, and iTunes would do whatever it needed to do to get everything cleaned up. So I changed the preferences to the hard drive location and nothing happened in the iTunes song list. I quit iTunes, moved all of the iTunes management files on the Mac to an untitled folder on the desktop, and restarted the computer. When I open iTunes I get the same 600 songs from the cloud even though the preferences say the program is looking to the hard drive. I need someone to help me walk thru what I need to do get this done. I need the MacBook Air for work and the music stuff is just in the way. I’ve owned Macs for 35 years and can’t recall ever having this happen before when I got a new computer or changed to a computer I wanted to use for music. Sorry for the length here.