Which of the following is the largest volume?
a) 4.0 x 10^1 m^3
b) 3.8 x 10^7 cm^3
c) 3.8 x 10^5 dm^3
d) 3.8 x 10^8 mm^3

I will use this conversion:

1m = 1000 mm => 1 = 1m / 1000mm

1 m = 100 cm=> 1 = 1m / 100cm

1m = 10 dm=> 1 = 1m / 10 dm

So,

B) 3.8 * 10^7 cm^3 = 3.8 * 10^7 cm^3 * [1m / 100cm]^3 = 38 m^3

C) 3.8 * 10^5 dm^3 * [1m / 10 dm]^3 = 380 m^3

D) 3.8 * 10^8 mm^3 * [1m / 1000 mm]^3 = 0.38 m^3

Now you can compare the four volumes and conclude which is the largest.

option C) 3.8 * 10^5 dm^3