That pump is way too big for your pool but to answer your question about cost, from the Hayward site that pump is wired for 120 volts so assuming the 12 amps is the actual running current that is 120 x 12 = 1440 watts. Electricity is billed on a kilowatt-hour basis and that number can be found on your electric bill or from your power company. Probably on the order of 15 cents per KWh. The 15 cents is a WAG (Wild A-- Guess) and varies considerably on locality. So, the 1440 watts for 1 hour is 1.44 KWh so you can get a rough estimate on cost knowing how many hours you run it.
Hope this helps.
Al