kilo, mega, giga, tera, peta, exa, zetta, yotta..
these are all SI prefixes, each multiply by 1000.
You might be a little confused since binary base values however are different, requiring powers of 2 instead of powers of 10.. that is why its 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, etc. This is why 1024 bytes = 1 kilobyte, since it does not conform with SI. However this is not the case with hashing.
One gigahash would be equal to 1000 megahashes, which is equal to 1,000,000 kilohashes.
To find how many bitcoins you are getting per kilohash you could divide the bitcoins you get per gigahash by 1,000,000.
If you would like to calculate how many hashes you will create over a certain period of time (in seconds), simply multiply rate * seconds to get the expected number of hashes to be preformed in this period of time.
Because of difficulty changes, you can only estimate your payout rate until the next difficulty change. The difficulty statistics can be found here: https://bitcoinwisdom.com/bitcoin/difficulty
More information on what bitcoin difficulty is can be found here: https://en.bitcoin.it/wiki/Difficulty
If you are trying to use a mining calculator, such as http://www.alloscomp.com/bitcoin/calculator you only need to put your hashrate/s, as it preforms calculations based on this and not the total amount of hashes.