$(C)$ có tâm $I(1;-2)$, Bán kính: $R=1$
$V_{(O,3)}I(1;-2)=I'(a,b)$
$\vec{OI'}=3\vec{OI}$
$\vec{OI}=(1;-2)$; $\vec{OI'}=(a;b)$
$\Rightarrow\left\{ \begin{array}{l} a=3.1=3 \\ b=3.(-2)=-6 \end{array} \right .$
$\Rightarrow I'(3;-6)$
$R'=3R=3.1=3$
$(C'): (x-3)^2+(y+6)^2=9$