Note:
Nickel ore has a density of about 1.6 g/cm³.
This is equivalent to
(1.6 x 10⁻³ kg)/(10⁻² m/cm)³ = 1600 kg/m³
Because the ore yields 32.6% of nickel by mass,
1600 kg ore will yield 1600*0.326 = 521.6 kg of nickel.
Therefore, 75.0 g of nickel requires
[(75 x 10⁻³ kg)/(521.6 kg)]*(1600 kg ore)
= 0.23 kg ore
Answer: 0.23 kg of ore