Hi.
a. Let's start by converting cubic meters to cubic kilometers. To do that, I look up the conversion factor, which is that there are 1.0 x 109 cubic meters in each cubic kilometer.
1.0 x 1023 m3 x 1.0 km3 / 1.0 x 109 m3 = 1.0 x 1014 km3
b. Now we have to convert from cubic meters to cubic miles. Again, I look up the conversion factor, which is that one cubic mile is equal to 4.168 x 109 cubic meters.
1.0 x 1023 m3 x 1.0 cubic mile / 4.168 x 109 m3 = 2.4 x 1033 cubic miles
c. This time we will go from cubic meters to cubic centimeters. Since the unit to which we will convert is smaller than the one from which we convert, we expect the magnitude to increase. The conversion factor is 1,000,000 cubic centimeters per cubic meter.
1.0 x 1023 m3 x 1.0 x 106 cm3 / 1.0 m3 = 1.0 x 1029 cm3