If you had used MB's computer node to move the files, everything would be fine. You can't expect MB to know where you moved the files to if you did it using a file explorer or some such animal.
I think what you now need to do is search and replace (old path to new path) using a text editor such as Notebook++. Make backup copies of the playlists before you start and edit only one playlist. If it works as expected, then do the rest.