Do you know how to find the surface area of a single rectangular prism? (Do you know what a "rectangular prism" is?). There are several different ways you can "cut" this figure into three rectangular prisms but the simplest is to cut off the two parts that "rise above" the rest. Note that there will be four faces, or parts of faces, of the three rectangular prisms that fit together and so will not contribute to the surface area of the entire thing.