
Don't delete anything in your collection. You're going to lose loops, cues and grid info.
Move all your music files to one folder. MacOS has a search built-in to search for all your music files.
In Rekordbox make sure you have the folder selected where all the tracks are in the auto relocate section. https://www.youtube.com/watch?v=LF_JKMnQEzQ
With you method you are describing you will lose everything in your collection because you're deleting everything in your collection. And you don't want that.