To find the perimeter, we have to find AB which is the hypothenuse of the right triangle ADB. Let's use Pythagorean's Theorem.

Replacing the given values, we have.
![\begin{gathered} AB^2=4^2+3^2 \\ AB=\sqrt[]{16+9}=\sqrt[]{25} \\ AB=5 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/4y7imeq0uxx875g6nbqarbfgyuskp3x5jh.png)
Given that AB = BC, then BC = 5.
Moreover, remember that the perimeter is the sum of all sides.

Hence, the perimeter is 16 units long.