Answer
The fill in the blank is
$\sqrt[n] {a^m}$.
Work Step by Step
The given expression is
$a^{\frac{m}{n}}$
The denominator of $\frac{m}{n}$ is the root, and the numerator is the exponent.
Hence, the root is $n$ and the exponent is $m$.
We can write $\sqrt[n] {a^m}$.
