No need to convert them. Just stick a 120 on the supply side and it's a go. IF you have a 620 take up spool. Big thing is to clean the things. I bet on average many have been sitting unused for years.
Loading for me was VERY wierd until I read the manual. Then it was easy.
I'm not saying it's the worlds greatest holder but mine worked just fine once it was cleaned up. FWIW mine is the 4x5 model but I don't think that makes much if any difference.