First, thank you so much for taking in the molly before your friend killed it I am so glad that you took in the molly,.
second, Mollys do not lay eggs unlike other fish, they give birth to live fish, pregnant mollies usually give birth after 45 to 60 days, the number of frys( baby fish) usually depends on the age of the molly the more mature the molly is the more frys, they typically give birth to 10-100 frys, after the frys are born the parents do not provide any care to the frys, the good news is that just after a few hours after their birth they will be able to feed and swim, the bad news is usually the mom after she gives birth she may eat the frys depending on how hungry she is but the frys normally after they are born they imddeilty look for somewhere to hide so you have to have many places a fry could hide in to avoid being eaten or you separate the frys from the mom but its better to keep them in the same aquarium just get more hides you could get real plants or fake plants but real plants are much better, but even with hides some frys would be eaten I know it may seem cruel but it is a natural way to control the growth of your molly population.
Change out 10-30% of their water each week to keep the tank clean, its best preferred to use a sponge filter so they will not be drawn in by the current, you will also need a heater the ideal temperature is 70 to 82°F (21 to 27.7°C).
Feeding,
Small meals are best. Do not feed your fish any more than they can consume in three to five minutes. brine shrimp or worms are always a hit, but you could use dry food.