They're all male.
It's extremely easy to tell if dwarfs are male or female because only the males have the bright colors. Females are silvery or brownish with irridescent shades and sometimes faint stripes. You can also tell because mature males have longer fins. Someone here once described them as 'bulbous' (the anal fin especialy) and I've used that word ever since as that seems a very fitting description. Females also look more 'discus-shaped' with a deeper body and, when viewed from above, are quite significantly wider. Males are longer looking, more lean and stream-lined.
If your tank is 30 gallons or more, the 3 males should co-exist quite happily as long as no other gouramies or top-dwelling fish are added and assuming they have enough places to hide in and settle individual, undisputed territories. Adding floating plants (but don't fully cover the surface as, without access to air, they'll drown), tall-growing rooted plants and some caves relatively high up in the tank are very helpful. You may also want to try feeding in several places at the same time so that not all the males are forced into the same territory when it's time to eat.