if the diameter of the can is 6 cm, then its radius is half that, or 3 cm.
[tex]\bf \textit{surface area of a cylinder}\\\\ SA=2\pi r(h+r)~~ \begin{cases} r=radius\\ h=height\\ \cline{1-1} r=3\\ h=12 \end{cases}\implies SA=2\pi (3)(12+3) \\\\\\ SA=6\pi (15)\implies SA=90\pi \implies SA\approx 282.74[/tex]