If these are all Singer machines, then you have two 127's and a 66 in treadles and the hand crank is probably a 28.
If those are the correct model numbers, they all take the "standard" 15X1 needle system. (Singer #2020, Organ HA X 1)
I order them from ctusa or eBay for $12-15 per hundred in the sizes I use the most - 10, 11 & 12, and by the ten-pack for the sizes I don't use so much - 9, 14, 16, 18 & up.
For wovens, you'll want "sharps" and for knits, you'll want ball point needles. After those two main points, there are tons of other options for types of needle - topstitching, embroidery, denim, etc.
I never buy the so-called "universal" needles - they don't sew wovens as well as sharps and they don't sew knits as well as ball points. (or even as well as sharps, sometimes!) Dern things are just a pain in the neck.
Hope you get the "ol' gals" sewing... they're happy when you put them to work. :)