I am going to add that you shouldn't leave the mom in small tank for very long IMO. The OP said they put the molly is 3g tank. Thats fine, but don't leave her in there for more than a couple of days. That tank is small and the mom needs to swim around to really get the process going. Being put into a small tank is stressful for the mom, so if she doesn't drop fry within a couple days, put her back in the display tank for a bit. You can put her in the birthing tank again.
Also, I prefer to keep to my fry in filtered, heated environments. I do know that some people use vases and jars and such. To each his own. I am just going to add that the fry will grow better IMO in warmer water versus in a vase or jar that is unheated.
Another note for the OP, how many mollies do you have? They should be kept in ratios of at 2 females for every male (1m:3f is even better) IMO to avoid stressingthe females too much. The males tend to tbe relentless in pursuing the females, so if you keep several females for every 1 male, the attention is spread out and each female gets a break.