Check the picture below.
so the perimeter will be, 3+3+3+3+3+3 plus the circumference of those two semi-circles, now, the two semi-circles together form a whole circle, whose radius is 3, so the perimeter will be 3+3+3+3+3+3 plus the circumference of a full circle with a radius of 3.
[tex]\bf 3+3+3+3+3+3+\stackrel{C=2\pi r}{2\pi (3)}\implies 18+6\pi \implies \stackrel{~\hfill \pi =3.14}{18+18.84}\implies 36.84[/tex]
