Answer
$ \boxed{\frac{mq^2}{n^{4}}}$
Work Step by Step
If a power on the numerator has a negative exponent, it can move to the denominator with a positive exponent, and if a power on the denominator has a negative exponent, it can move to the numerator with a positive exponent.
So,
$$ \frac{mn^{-4}}{p^0q^{-2}} = \frac{mq^2}{p^0n^{4}}$$
Anything to the power $0$ is always $1$. Therefore, $p^0$ must be $1$.
Therefore,
$$\frac{mq^2}{p^0n^{4}} = \boxed{\frac{mq^2}{n^{4}}}$$
