basically just get each surface area then add them all up. this prism, not a cube, has 6 sides.
you have all 3 sides measurement that you need, lets do the one that is facing us
6×7=42 cm^2
now the opposite side of this surface area we just did have the same area measurement, so times 2
42×2=84cm^2
two to go, lets do the surface on the right side
3×7=21cm^2
again, oppisite side is the same, times 2
21×2=42cm^2
bottom surface area
3×6=18cm^2
then times 2
18×2=36cm^2
bow add all of them up
84+42+36=162cm^2
total surface area is 162cm^2