The side length of the cube will only go up by a factor of 2.
Think about it like finding the volume of a cube in reverse:
\(volume = side^3 = side * side * side\)
If we multiply the left and right sides of this equation by 8:
\(8 * volume = 8 * (side*side*side)\)
And try to "distribute" the 8 by splitting it up into three 2's:
\(8*volume = 2*2*2*(side*side*side)\)
\(8*volume = 2*side * 2*side * 2*side\)\(8*volume = (2*side) * (2*side) * (2*side)\)\(8*volume = (2*side)^3\)
We can see the side length only doubles.