Answer
Volume of a Sphere = ${(4/3) * pi * (radius)^3}$
therefore;
${pi*(3.446*10^{11}})$ or about
${1.083*10^{12}}$ cubic kilometers
Work Step by Step
First of all, 1 kilometer = 1000 m so Earth's radius = 6370 kilometers
and Volume of a Sphere = (4/3) * pi * (radius)^3
