Answer
$7\times 10^6 V/m$
Work Step by Step
The magnitude of the electric field, assumed to be constant, is the voltage change divided by the distance.
$$|E|=\frac{\Delta V}{\Delta x}$$
$$=\frac{70 \times10^{-3}V}{1.0\times 10^{-8}m}=7.0\times 10^6 V/m$$
