For any value of e, (the edge length), just cube it to get the volume. Easy
V(-2) = -8 V(-1) = -1 V(0) = 0 V(1) = 1 V(2) = 8 V(3) would be 27...etc
It doesn't make sense to use a negative or zero value for e (since you can't have a length like that), so technically there should be a restriction of e > 0.
To find the edge length given the volume, we would just solve for e.
V = e³ Take the cube root of each side... ∛V = ∛e³ ∛V = e