Do you mean scientific notation?
If so,
A number is written in scientific notation when a number between 1 and 10 is multiplied by a power of 10. For example, 650,000,000 can be written in scientific notation as 6.5 ✕ 10^8.
In order to write a number in scientific notation, I suggest you place the tip of your pencil right after the last digit in the number.
Then go backwards, counting each jump to the next number (this will be your exponent number).
You will go backwards until you reach your first NON-ZERO digit, which is where you will place the decimal point.
Multiply the decimal you now have by 10 (multiplying by 10 applies every time!) and then to the power of however many spaces you went back.