The answer is 3.58 x 1013
1. Write all significant figures as a number between 1 and 10. Do this by putting a decimal point just to the right of the first non-zero digit.
2. Count the number of decimal places needed to get back to the original starting number, while noting the direction you must move to do that.
3. Write step one times step two, but write step two in exponential notation. The number of decimal places moved gives the exponent value and the direction moved gives the sign (left = positive; right = negative).
Note that the exponent indicates HOW MANY places the decimal point was moved and the sign of the exponent indicates the DIRECTION of the movement.
There were then two graphics showing with arrows the movement of the decimal point.
In this problem, the decimal point was moved 13 places to the LEFT (positive exponent).