You reverse what you did, so first you go 5 units down which makes the coordinates (9,1) then you move 3 units left which then is (6,1). Then you go 4 units up which lets you end out at (6,5).
1) calculate the volume of the tri prism 2) find area of the base face 3) find the height 4) multiply area of the triangle base time height 5) answer will be in cubic units