You multiply 10x10x10x10x10x10 (10 appears 6 times as a factor).
10^6=1 000 000 = 1 million
1,000,000 Decimal form avoids fractions. For example, 1/2 is .5 in decimal form. 10^6 is 10x10x10x10x10x10. This is 1,000,000. (Since you are multiplying tens, you can just add the zeros together.)
Each spot on the license plate could have one of 10 digits (0-9). There are six spots. You could have 10X10X10X10X10x10 different plates. Realistacally, they probably wouldn't give out all zeroes though.
A kWh is a kilowatt-hour, which is a unit of Energy or Work. Your utility company measures the amount of electrical energy you use each month in kilowatt-hours. A megawatt or MW is a unit of Power, which is the rate at which energy is used. Also a megawatt is 1000 kilowatts. Therefore, a kWh is one kW of power used for a full hour. A kWh is a MW of power used for 3.6 seconds (1/1000 of an hour).
if you ignore the initial 5times for now there is actually a button for this kind of calculation on your calculator(scientific- but still cheap mine was £10) it is shown as x! in this case 10! is 3628800 and remembering the initial 5times= 18144000 this kind of calculations are used for figuring possible combinations of letters and numbers.