In that box we have 9 squares. One of the square has 1cm for all sides. That means the perimeter of one of the boxes is 4cm. For the 9 boxes, we have 4x 9= 36cm I think?

A square with $1 \text{ cm}$ for all sides has a perimeter of $4 \times 1 \text{ cm} = 4 \text{ cm}$.

If you add up the perimeters of 9 squares, each $4 \text{ cm}$, you get:

So, your calculation of $36 \text{ cm}$ is correct if you are summing the perimeters of 9 individual, disconnected squares.

However, when squares are placed together to form a larger shape (like "in that box"), the sides where they touch are no longer part of the outer perimeter of the combined shape.

If 9 squares, each $1 \text{ cm}$ by $1 \text{ cm}$, are arranged to form a larger square (a $3 \times 3$ grid), the side length of this larger square would be:

The perimeter of this larger square is:

So, if the 9 squares form a larger $3 \times 3$ square, the perimeter of that larger shape is $\boxed{\text{12 cm}}$.