If the first question is indicating that the diameter of mercury is 4.88x10^3 kilometers, then to put this in standard notation you would move the decimal point three places to the right, which gives you 4880 kilometers.
For the second question, you have to count how many places to the right the decimal place needs to be moved to have a number in the ones place. In this case, that number is 4. Scientific notation would be 1.96x10^(-4) meters. For any number where the value is less than one, the ten will be to a negative power.
