how do I get the small exponent number which is lower than the whole number?
When you raise a number or a variable to the 2nd power, what does that mean? Or n^2 in this case. Of course it means you are squaring it or multiplying it by itself. Let us use a number such as 5.
5^2 means 5 x 5=25. Now, what the reverse process for that? It is of course taking the square root of 25 =5.
Now, suppose you had something like this: 5^n=625. How would you find n? You would take the logs of both sides: n x log(5) = log(625)=n =log(625) / log(5)=4.