The sqrt of (34 m^4) is sqrt(34) times sqrt(m^4).
The sqrt of m^4 is easy ... that's just m^2 .
The other part is more messy. There's not much you can do with it.
sqrt(34) = sqrt(17) times sqrt(2).
That doesn't help make it any simpler.
You might as well just leave it as sqrt(34).
Then the final, simplified form of the original expression is
m^2 sqrt(34)