idk, but I remember this one place that had a Flower horn coverted to live in salt water. They said the process took at least 6 month or more. They have to do it slowly by adding current percentage of salt water at a time.. idk about mollie tho..
You can probably acclimate them over a couple of hours. I did it with guppies. The only ting you want to consider is dripping them very slowly, then once you get them in SW, gut feed them nothing but marine flakes.