We start at the farthest right of this number, then shifting it 6 places to the left until we get only one whole digit in our answer. In this case are whole digit would be the number "3" from the millions place written out as 3.01 x 10^6. Because we started at the right of the number and shifted to the left 6 times, we get a positive exponent of "6."
Here is an example of a negative exponent in scientific notation: