Steps to solve the problem:

1, because it is composed of two identical squares, it is composed of the side lengths of six small squares.

2. Because it is composed of the side lengths of six small squares, and the side lengths of the squares are equal, we can calculate the side length of each small square: 30 ÷ 6 = 5 (cm).

2. Because the side length of each small square is 5cm, the circumference of each small square is 5x4 = 20 (cm).

Extended data:

Square perimeter formula

Formula description:

C=4a

In the formula, a is the side length of the square and c is the perimeter of the square.