I'm trying to prove
If $m^n=a^pb^q$ for positive integers $m,n,a$ and $b$ and different primes $p$ and $q$ (with $p+q \neq n$), then each of $a$, $b$ and $m$ must be a power of some integer $x$.
I'm trying to prove
If $m^n=a^pb^q$ for positive integers $m,n,a$ and $b$ and different primes $p$ and $q$ (with $p+q \neq n$), then each of $a$, $b$ and $m$ must be a power of some integer $x$.
$4^7=8^3\cdot2^5$ is a counterexample to your claim in which $p$ and $q$ are distinct.