So I'm working out the volume and have 0.5mm, 10km & 100km.

I've changed 0.5mm into 5.0x10^-6 km

So it works out as 5.0x10^-6 km x 10km x 100km = 5.0x10^-4 km^3

I also need to work out mass using the desity value of 1x10^3 kg m^-3 but do I need to convert any value like I did with the 0.5mm and what would the measurement be in? kg m^-3 x km^3 becomes what?