The power of a number says to us how many times to use a number in a multiplication. So this concept is related to exponents, So the present exercise is asking for a number that is equals 256, that is, we need to find a number [tex]n[/tex] such that [tex]n[/tex] to the fourth power in fact equals 256. Therefore:
[tex]256=n^{4} \\ \therefore n=\sqrt[4]{256} \rightarrow \boxed{n=4}[/tex]
So we have found the searched number and it is [tex]n=4[/tex] as you can see in the equation above.