The above video shows a teacher explaining how to find the surface area of a rectangular prism.
The video above shows how to find the surface area and volume of a triangular prism. It's a very good explanation, but you need to know the Pythagorean theorem to understand it fully.
The video above is a visual explanation about how people figured out the formulas for the surface area of rectangular and triangular prisms and cylinders.
Use these search terms to find additional resources:
surface area of cube
surface area of cuboid
surface area of rectangular prism
surface area of triangular prism