To find area $ A $ use formula:
$$ A = 2 l h + 2 l w + 2 h w $$After substituting $l = 6\, \text{cm}$, $w = 5\, \text{cm}$ and $h = 3\, \text{cm}$ we have:
$$ A = 2 \cdot 6\, \text{cm} \cdot 5\, \text{cm} + 2 \cdot 6\, \text{cm} \cdot 3\, \text{cm} + 2 \cdot 5\, \text{cm} \cdot 3\, \text{cm} $$$$ A = 60\, \text{cm}^2 + 36\, \text{cm}^2 + 30\, \text{cm}^2 $$$$ A = 126\, \text{cm}^2 $$