I love 'name that fish' You've got a couple of mollys, one sailfin and one regular. It's a bit hard to tell from the photo but the sailfin (the one with the big dorsal fin) looks like he might be a male.
You have a pair: a male and a female. Both are silver coloured sailfin mollies. Female has the rounded fin under her belly, male has a rod shaped fin. She will be pregnant already, if past experience is anything to go by!