I can only imagine that "convert to derivative form" means " take the derivative of ...", since, if you do, then the other given information, g(x) and g'(x) at x = 3, becomes usable.
Taking the derivative of 1/g^2(x), (= g^(-2)(x))
d(g^(-2))/dx = (d(g^(-2))/dg).(dg/dx) = (-2)(g^(-3))g'
Letting g(3) = a and g'(3) = b, then
(-2)(g^(-3))g' at x = 3 is: (-2)(a^(-3))(b) = -2b/a^3
Answer: -2b/a^3