Yes, or alternatively, if it were an irregular prism, cross-sectional area x height.

Now, you have a measure of area in your original problem, and a height, so what's the volume of water falling on your land? You may find it easier to convert figures to metric, so 1 inch is 2.54 cm, and one acre is, well, I'll let you do that

Once you have the volume you can then use the density of water to calculate the mass of water falling, and consequently the number of moles falling.

You then have the amount of heat it takes to vaporise 1 mol of water, and the number of moles, so Robert is your parent's male sibling, no?