If you live north of equator this is wrong time of yr to be starting melons. Even with a greenhouse it would be difficult to make a crop. You'd need lots of sun and 60F night temperatures. Very expensive melons.

Transplant after they get two true leaves.

I live in South Carolina I will watch for two leaves, how do I transplant. Can they all go back into a larger pot? Have heater in sun room and flours ant lights. Any suggestions. They look a little larger

Just cut off all but one or two. Then when bigger up pot if needed. You won't make an edible fruit this time of yr. It will be an ornamental only. More plants just makes any fruit set even more unlikely. Two or three at most.

Sorry, I don't understand, new at this, please explain in detail.

Melons need high light and long hot days to make large sweet fruit. You can't duplicate that this time of yr. You would be lucky to get small fruit with no taste. Outdoors I allow about 20 to 50 sq ft per plant sometimes even more.

I was hoping to grow large enough to transport to a larger pot. Don't expect melons at this time.just trying to grow large enough from seeds and wait until spring to transportplant them.

Start your seedlings for transplanting a few weeks before last frost in spring. The current plants will not make it to spring and still produce fruit next summer.

As said above.....it won't work this time of year.Melons don't transplant well when they have more than 2 leaves.
You can't start them now and transplant next spring.Waste of time and effort.Wait until 4 weeks before you want to put them in the ground and start them then.

Grow lights, lots and lots of grow lights. Seedlings are cheap, grow lights are expensive. Off with their heads!

See, if you let people know where you reside as opposed to what state you live in you can get accurate responses (maybe?) for where you live.

Here is a link that might be useful: South Carolina Planting Chart links