Since you’re multiplying n^-6 and n^3, you can add the exponents: -6+3 = -3
n^-6 * n^3 = n^-3
If you need to finish without having a negative exponent in your answer, then remember a negative exponent means that factor is on the wrong side of the fraction.
n^-3 = n^-3 / 1 = 1/n^3
when the factor moves to the other side of the fraction, the side of the exponent changes.