I think you should divide by 1000.
I strongly suspect that you are attempting to convert a mass in grams into a mass in kilograms. Relative atomic masses are usually quoted in grams, e.g. carbon is 12.0 g and lead is 207 g. (Relative atomic mass for an element is the mass of one mole of the element.). But in order to perform a calculation with the relative atomic mass it needs to be converted into kilograms.
Here are the conversion factors:
So here are the two relative atomic masses that I quoted above in kilograms:
Carbon = 0.012 kg
Lead = 0.207 kg