The question is,
Which group of order $12$ is isomorphic to $S_3 \times C_2$ ?
I know that this group is a non-abelian group so it's not isomorphic to $C_4 \times C_3$ and $C_2 \times C_2 \times C_3$.
I explicitly show that this group contains three element of order 3. Is there any general way to show this one?