You figured it out correctly, good job!
Nevertheless, let me answer the question, so that the homepage is clean and someone else might need some explanation.
We want to compute
We can break the root of a product into the product of the roots:
The square root of -1000 is -10, because
As for the exponents of the variables, taking the n-th root means to divide the exponent by n. So, in our case, we have to divide the exponents by 3:
So, the final answer is