It's a flattened pyramid. Like if you took a pyramid shaped box and made it flat. So you can calculate the area of all the sides and then add them together to get the surface area.
Area's of flattened sides:
Top side: 22*6 = 132 m²
Middle side: 22*8 = 176 m²
Bottom side: 22*10 = 220 m²
both triangle sides make square: 6*8 = 48 m²
Total surface area:
132 + 176 + 220 + 48 = 576 m²