iTunes: how to save old playlists and play counts if location of mp3 has been changed?

Copying the files independently in Finder doesn't let iTunes know they've been copied. If you then remove the source drive iTunes won't be able to find the files. Instead you should reconnect the drive and restart iTunes which should mean that it can see the tracks once more. Then choose a new location for your media folder. Typically this would be ~/Music/iTunes/iTunes Media where ~ is your user's home folder, assuming you have space on the drive, otherwise <Volume>/iTunes/iTunes Media is a good choice. Having chosen a new media folder you use File > Library > Organize Library > Consolidate Files to tell iTunes to create new copies in that location and update the database to reference the new copies instead of the old ones. Ideally your library files (iTunes Library.itl, .itdb files, and Album Artwork folder) will be in the iTunes folder that contains iTunes Media. If that isn't the case due to past choices then with iTunes closed you can copy the active library files there, then hold down option as you launch iTunes and choose the iTunes Library.itl file on the new path. Keeping your library in this shape makes it easy to move the entire iTunes folder from one location or computer to another where it can be opened with the option-start-iTunes method and all of its file references should adjust automatically.

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