Welcome to Reef2Reef!
First, I personally don't like those multi-test dip strips. Even if they say they are for aquariums, they are usually rebranded swimming pool or drinking water tests, and in my experience not every accurate or easy to read. I would suggest you get a decent aquarium test kit. If you're just getting started, you'll want to be able to test primarily for ammonia and secondarily for nitrate at this time. Salifert makes inexpensive, easy to use, and reliable test kits if you're looking for a suggestion. If you can only get one kit now, get the ammonia test kit.
We would need a little more information in order to help you with your new tank. Please let us know how you started your tank. Did you use dead, dry rocks and sand, or did you purchase some or all live rock from a local store? If you used dry rocks, did you add any kind of beneficial bacteria product, such as Dr. Tim's One and Only, Microbacter7 or Fritz Turbo Start to name a few? Did you add a source of ammonia, such as bottled ammonium chloride or fish food?
I assume the Mollies were acclimated to saltwater? I personally wouldn't add any more fish until you are sure your tank is fully cycled. Typically, that takes A LOT longer than 3 days, unless you use live rock, pre-cycled bio media, or a quick-start bacteria product, like the Fritz Turbo Start.
If you can post back with a little more information about your tank and how you set it up, I'm sure someone will point you in the right direction.
Best of luck with your tank!