How much CO2 would be produced if 1.00 gallon of propane was combusted in an excess of oxygen?

We were told that to solve this we would convert gallons to liters, use density to convert liters to grams, and then use molar m to convert grams to moles. I believe I have it fairly figured out but I cant figure out if at the end I should divide grams by moles or moles by grams. PLease help if you can :)