Answer: 3.156 * 10^7
Explanation: I do not really understand your question. You answered it yourself!
Scientific notation shortens large numbers. The number right after the decimal point can only be between 1 and 9, which you did correctly. When converting to scientific notation, the exponent of ten is based on how many places you moved the decimal and the direction you moved it (left, positive; right, negative). In this case, the exponent of ten is a positive seven.
You did everything correctly :) Good job!
