The stack of small cubes would be 100 kilometers high.
The volume of the box is given by multiplying the length, width, and height. In this case, the length is 1 m, the width is 2 m, and the height is 5 m. Therefore, the total volume is 1 × 2 × 5 = 10 m³. Since each small cube has a volume of 1 cm³, we can calculate the number of cubes by dividing the volume of the box by the volume of a single cube. So, 10 m³ is equal to 10,000,000 cm³. Finally, to find the height of the stack, we need to divide 10,000,000 cm³ by the height of a single cube, which is 1 cm. The stack would be 10,000,000 cm or 100 kilometers high.