You will have to use the equation F_g = GMm/r² where F_g is the force of gravity (what you’re finding), G = the gravitational constant (this can be looked up, something like 6.673x10^-11 Nm² /kg² or if it’s specified what yours rounds to), M = mass of observed planet, m = mass of observed object on observed planet, and r² = radius of the observed planet squared. By using this equation after finding the mass and radius of the observed planet, you will be able to find its force of gravity and can then use that to find the original weight of the object when unaffected by gravity on the observed planet. You can then take the original weight of the object and multiply it by the force of gravity on earth to find your answer.