Hi there and welcome to the forum.
Body sweeling can happen for a number of reasons like a big meal, inpending birth or egg release depending on the species, tumors abcesses and in your mollies case a condition called dropsy. In most of those conditions we see a generalized swelling of the body because the swelling is comming from the inside. With dropsy the tissues themselves swell with fluid so as the skin gets swollen it pulls apart the scales and they stick out like a pine cone effect.
Dropsy is not really a disease but a symptom of disease. Unfortunatly it is not a good sign at all. Once this happens it is usually a sign of internal organ failure. Most often kidney but also liver
Here is a nice link from the main site to help explain.
sorry to be the barer of bad news but it doesnt look good. That doesnt mean its not worth trying. If you have an empty tank I would set it up seperatly as a hospital treatment tank and try one of the medications reccomended on the link. If you are in the US let me know as there are a lot more options available.
If you dont have a hosptial tank available let us know how big your tank is and what else is in there and we can help makes sure the treatments are safe for all the fish species in your tank. Some species can be particularly sensative to certain medications.