Вам нужен только один Scanner
. И просто замените
System.out.printf("Volume of the cuboid (Length: " +
length + "/Height: " + height +
"/ Width: " + width + ") is " + cuboidVolume);
на что-то вроде
System.out.printf("Volume of the cuboid (Length: "
+ "%.2f/Height: %.2f/ Width: %.2f) is %.2f%n",
length, height, width, cuboidVolume);