Welcome! I am going to add in here that it can be difficult to tell the exact time with livebearers. They are capable of storing sperm, so just because you saw "it" happen does not mean it will necessarily be a month from then.
Also, if you bought the female from a place where she was housed with males, I can pretty much guarantee she is already storing sperm anyhow.
A couple of notes: YOu can start as big of a nursery as you want. The breeding nets are really for people do not have a nursery tank, so if you have another tank, thats better than a breeding net. If your nursey tank in less than 20g, only ever leave the female in there are for a few days at a time at a time. Mollies are active and messy, so being in small environments is stressful to them. Also, they need to be able to swim arouond to get the process going.
The molly parents can and do eat the babies. If you leave the mom in with new babies, they will get eaten. Lots of plant (real or fake) cover is good for nursery tanks so the fry can all hide.
Also, you said you have a molly pair. I just going to assume that you only have those 2 mollies (if I am incorrect, ignore this). Mollies and other livebearers should be kept in the ratio of 1m for every 2-3 females. The males are relentless in their romantic pursuits, so the females usually get stressed out which is really bad for them. More females means the male's attention will be spread out and every girl gets a break.
Good luck! Feel free to ask any more questions or add any more info. Also, we love pictures here!