I got this question on my homework and completed it, however, I would just like to check if my answer is correct or not. I need to convert it to units of cubic meters.
Density = 0.81 g/mL
1 gram = 0.001 kilograms 1 milliliter = 1e-6 cubic meters

Thank you in advance!
You need to use the $0.81$ g/ml. Your division is correct.