Change location of group of referenced files

Set your iTunes music/media folder to the location you want the movies to go. Highlight all the movies you want to move to this location, right-click and choose "Consolidate Tracks". They will be copied to the new location, and iTunes will reference them from there. You can then delete the movies from their original location to free up space, then change your iTunes music/media folder back to whatever it is you want it to be.