No, that's the perimeter. The area is the 2D space the shape takes up. There are different ways to work it out for different shapes, but the easiest way is to split your shapes up into rectangles and then multiply the length by the width.

So if you have a rectangle of 50mm by 120mm, your area is 50 x 120 = 6000 mm^2. Or if you want to get the area in metres, you convert the sides to metres first: 50/1000 = 0.05m, 120/1000 = 0.12m so then 0.05 x 0.12 = 0.006 m^2.

For right-angled triangles, you multiply the two sides together that form the right-angle, and then halve that to get your area.

Once you've found the areas for all your bits, add them together and then multiply that result by the thickness of your material to get volume. Then multiply your volume by the density to get mass.