This is a comment from yahoo answers: The six-16 uses type 616 film, a close relative of 116 film. 616 film production stopped some time in the 1970s, and 116 followed in the late 1980s. Unfortunately, 616 cameras are pretty much useless today except as shelf ornaments.
The six-20, though, uses(surprise) 620 film. Unfortunately, 620 hasn't been factory-made since about 1996.
Fortunately, though, 620 is really just 120 on a different size spool. There are still brand new cameras being made which use 120 film, so 120 film is still quite available if you know where to look.
Please see the links below in the references section for sites with detailed instructions and pictures describing how to respool 120 film onto 620 spools.
You can order 120 film quite inexpensively from B&H Photo. I'd suggest starting with Kodak Tri-X 400 for black and white or Kodak Portra 400VC for color. Unless you have a pro lab in your area, you probably can't develop either of these locally. You can, however, drop them in the send off box at Walmart(for sure-I've done it myself) or maybe other retailers and they will come back in a few days((or maybe a week).
If you don't wish to go to the trouble of respooling, B&H will sell you 620 film which they have respooled themselves. If you're just wanting to use the camera once or twice, this might be the route to take. If you're going to use the camera several times, though, the signicant($5+) premium they charge over regular 120 adds up pretty quickly.
When I wound it up, the winder was turning and I could hear it turning,inside so I assume it works, I did not have film to check for sure. I bought it at an estate sale and that is all I know about it. thanks!