Answer
The electric force on the electron is in the -x direction.
Work Step by Step
We can find the strength of the electric field between $x = 5.0~cm$ and $x = 6.0~cm$:
$E = -\frac{\Delta V}{\Delta x}$
$E = -\frac{5.0~V-6.0~V}{0.060~m-0.050~m}$
$E = 100~V/m$
Since the electric field points from higher potential to lower potential, the electric field is in the +x direction.
Note that the charge on an electron is negative.
Since the electric force on a negative charge is in the opposite direction to the direction of the electric field, the electric force on the electron is in the -x direction.
