The following is (an adaptation of) theorem 10 of section 6.5 in Ahlfors "Complex Analysis".
> Suppose $\Omega \subset \Bbb C$ is an $n$-connected domain for which none of the connected components of $S^2 \setminus \Omega$ are a single point. Then for some real numbers $\lambda_1, ..., \lambda_{n-1}$, there is a one-to-one conformal mapping of $\Omega$ onto the annulus $1 < |w| < e^{\lambda_1}$ minus $n-2$ concetric arcs situated on the circles $|w| = e^{\lambda_i}$.
Reducing to the 2-connected case, this gives the theorem you want.