The amount of grams that are in one ounce is 28.35 grams.
So in 2 ounces you would have 56.70 ounces.
If we're talking about troy ounces there would be 31.1 grams in a troy ounce but in a true ounce there are 28.35 grams in one ounce.
Then to find out how many grams are in multiple ounces you just take the amount of grams in one ounce which is 28.35 grams and multiply that amount by the amount of ounces that you're trying to figure out.