Hi,
you can use Maintain Library or select the files you want to change and right-click then select Maintain Files and this will allow you to update the metadata of all the files using an automatic online metadata lookup. Make sure to select to update file properties and metadata and update all files and this will replace the existing metadata with the results of the online lookup.

If the path to your files remains the same then Mezzmo will be able to match the file with the metadata in the database. If the path to your files changes you can use http://www.mezzmo.com/wiki/doku.php?id=updating_your_mezzmo_library_after_mov ing_media_files&s[]=move&s[]=files