Star Ratings are saved in file tags by default, so if you've not changed the default settings, your files should contain the ratings. And you can Update library (from tags) to re-read them if you don't see them.
Another way to move files is to retain your existing library entries, delete the new ones from MC, and then use MC's Rename, Move & Copy tool in Database update-only mode to change the Filename (path) field for your existing entries. You can Find/Repalce the portion of the path that has changed. Same entries, now just pointing to a new location.