All of that fluff at the beginning is interesting, but completely irrelevant
to the question. The question is just asking for the mass of an object
that weighs 3.6N on Earth.
Weight = (mass) x (acceleration of gravity)
3.6N = (mass) x (9.8 m/s²)
Divide each side
by 9.8 m/s : Mass = 3.6N / 9.8 m/s² = 0.367 kilogram (rounded)