what are you trying to find? if you are looking for y, you have it already. e^3 is a constant.
remember that when you have y = b ^ x, this can be written as log_b y = x.
In this case, b = e, so log_e (y) = 3. Log to base e is written ln, so this becomes ln (y) = 3.
But, it's not clear to me what problem you are really trying to solve. Are you trying to solve for y? If so, just compute e^3 on your calculator, and that's the answer.