What I Know About Rectangular Prisms ;
A rectangular prism is a 3d object that has length, width and height.
When its flattened it is called a Net. A net is just how you look at the prism when you open it all up. The net helps you get the surface area.
To get the surface area you can find the area of all the parts (top, bottom, front, back, left side and r side) then add them all up. The easier way is to use formulas.
The formula for top and bottom is: LxWx2.
The formula for front and back is: LxHx2.
The formula for the two sides is: WxHx2.
After you find the area for those you add them all after. After you add them you have you're surface area. The surface area is usually cm² or something².
Another thing I learned was to get the volume. The volume for formula is LxWxH or BxH. The B stands for Base and the H stands for Height.
The volume is usually something³
For examples look at my scribe post