Working off of the previous comments, the definition of the voltage is the potential energy difference corresponding to two points separated by some short distance "dR" through an electric field "E":
V = -int (EdR) on the interval [0,R]
V = -E*R
Given in units, this is [V] = V = N*C^(-1)*m where [E] =N/C.
Rewriting for the units of the electric field (N/C), we get [E] = [V]/m = V/m
I hope that clarifies.