When you multiply by 10, 100, or 1000, you must move the decimal place over by how many zeroes there are. Once there is no more decimals, you add 0's to the end of the number until you are done.
For example, 5.6 x 1000
1000 has 3 zeroes.
That means we need to move the decimal spot 3 times.
5.6 x 1000 = 56 x 100
We got rid of the decimal but we still have 2 zeroes left. So now we just add 2 zeroes at the end of the number.
5.6 x 1000 = 56 x 100 = 5600
I hope that helps! :)