Depending on the format you are supplying us to have digitised you would need.
Video Tapes: Approx 1.5GB per 1hr of footage.
8mm / 16mm Movie Films: Approx 150MB per 50ft of film.
Photo Scans: Approx 5-10MB per image
Note: USB Drives hold less than stated on the packaging. ie 8GB USB drives only hold 7.2GB.