In one mole of Calcium Phosphate, or Ca3P2, there are 3 moles of Calcium. In order to find the grams needed to produce 3 moles of this molecule, you must first find the number of moles needed, and then convert to grams. If there are 3 moles of Ca in each mole of Calcium Phosphate, and you need 3 moles of it, then you would simply multiply 3x3=9.
Now that we know that 9 moles of Calcium are needed for this, we can convert to grams. When converting from moles to grams, simply multiply the number of moles by the molar mass. In this case, it would be as follows: 9moles x 40.078g/mol, which gives you 360.7 grams of Calcium.
Hope this helps!