That's very wrong
according to the question we need to find what -2^-3 is,
now get rid of the negative integer by converting the base(-2) to a fraction
so this implies (1/-2)^3
now it's easy, the answer is 1/-8
but we need to convert this to standard from, so we multiply both sides of the fraction by -1
so the final answer is -1/8
next time, try separating the exponents from the base with a parenthesis