$$ \begin{aligned} & \mathrm{c}=\frac{\mathrm{E}_0}{\mathrm{~B}_0} \Rightarrow \mathrm{E}_0=\mathrm{cB}_0 \\ & \mathrm{E}_0=\left(3 \times 10^8\right)\left(2 \times 10^{-8}\right) \\ & \mathrm{E}_0=6 \mathrm{Vm}^{-1} \end{aligned} $$ As, $\vec{B}=$ along $y$-axis $\vec{v}=$ along negative $x$-axis Hence $\vec{E}_0=$ along z-axis