Hi Faleigh....As a mollie veteran, I advise you to relax. Don't rush to move Mom to a separate tank as this could stress her to the point where she will abort/resorb the babies.
In the normal course of events, she will before long start to resemble the Hindenberg and you will become alarmed. Continue relaxing, this is normal. Then one day you will become alarmed because there are weird little wiggly things in your tank. Hand out cigars and continue to relax, that's the babies. They are quite self-sufficient at birth and really need no special care.
Caveat: you do not mention what other fish are in this tank. If they are "community" types you should be fine without any need to start netting wildly to get the babes into another tank. Just leave them where they are and they will duck and dodge anything they find worrisome. If you feed flake food just crush it up a little finer than usual and they can eat it without trouble. Ours have lived with other mollies (rumors of cannibalism are wildly exaggerated if not completely false IMHO), tetras, corys and platys. Nobody ate anybody. YMMV
If you just got Mom you probably don't know her age, and that has a lot of influence on how many she's likely to have. It could be anywhere from half a dozen if she's a first-timer to 20 or more if she's older. I would advise you to leave them where they are and let nature take its course. Even without carnivorous fish some of them will just die and you'll probably never see corpses. That's how it goes.
Next challenge in a few months will be to start noting sexes of the offspring. You need to catch all the males and either get them into another tank by themselves (where they will become hopelessly ***) or sell/trade them to your LFS. Otherwise the cycle will start again, as mollies have not quite evolved to understand the incest taboo.
Just remember the relaxing part. They are very cool fish and have been doing this a long time. You could wind up with some interesting fish after awhile depending on who Mom got friendly with in her earlier life. Enjoy.
