Answer:
72. If the second 3cm has some relevance, leave a note and I'll come back and modify my answer.
Explanation:
Givens
L = 6 cm
W = 3 cm
H = 2 cm
I don't know what the extra 3 cm is for.
Formula
SA = 2*L*W + 2*L*H + 2*H*W
SA = 2*6*3 + 2*6*2 + 2*2*3
SA = 36 + 24 + 12
SA = 72