When you divide a base with an exponent by a base with an exponent, you subtract the exponents together. (But you can only combine exponents when the bases are the same)
For example:

(You can't combine them as they have different bases of x and y)

When you have a negative exponent, you move the base with the negative exponent to the other side of the fraction to make the exponent positive.
For example:
or 
or
You can simplify the whole fraction or just "m" since you need to find the exponent of "m". I will simplify the whole fraction.

Make all the exponents positive
So the exponent of m = 5, your answer is the 3rd option