Answer
$V = 760 \mathrm{V}$
Work Step by Step
The electric field $E$ is related to the separated distance and the potential difference $V$ between the two plates. The separated distance here represents the radius of the sphere $R$ and the potential will be in the form \begin{aligned} V &=E R \\ &=(0.2\mathrm{m})(3800 \mathrm{V} / \mathrm{m}) \\ &=\boxed{760 \mathrm{V}} \end{aligned}