How do I update the location of my music library in iTunes?

A while ago I tried moving my music library from one Mac to another using an external hard drive but somehow botched the process, and now I don't know how to update all the file locations in iTunes (Apple Music) to point to a desired location. My new Macbook doesn't have enough space to store all my music so I have to store my library in an external drive. I was using an external HDD for a while but just I copied the files to an SD card and now I don't know how to get iTunes to recognize the new locations. I have tens of thousands of files so I can't update the file locations individually.

My current Mac is a 2015 MBP with Retina display so it is stuck on Monterey 12.7.6 with Apple Music version 1.2.5.7.

Most of my files have locations like this: file:///Volumes/2TB Passport/iTunes/iTunes Media/Music/George Harrison/Essentials/1-12 Handle With Care.mp3

For some reason some of the files have locations like this: /Macintosh HD/Users/rian/Music/Music 1/Media/Music/James Taylor/Essentials/1-01 Fire and Rain (2019 Remaster).mp3

I guess iTunes was importing my music to a location on the internal drive for a while.

So I need to do two operations.

1) The tens of thousands of files that iTunes thinks are on the 2TB Passport volume, they are now at the location: /Volumes/1TB microSD/iTunes/iTunes Media/Music/, and I would like iTunes to update where iTunes thinks those files are to the current location. (I still have copies of all the files on that passport drive too, in case it is necessary to delete the SD card folder and move the files from within iTunes.) And,

2) The several hundred files that currently live at /Macintosh HD/Users/rian/Music/Music 1/Media/Music/, I would like to move those files to the same location as 1), /Volumes/1TB microSD/iTunes/iTunes Media/Music/ , so that all my music files can live happily together in the same folder on my SD card.

How can I do this? Thank you.