Note that the electric force is conservative, so there are no losses to the total mechanical energy: energy is conserved.

So the initial electrical potential energy (not to be confused with the electric potential) will be equal to the final kinetic energy.

I get .

Note: This speed is right on the edge of what I would consider using Special Relativity for. (About a tenth of the speed of light.) Please make sure that your instructor does not want you to use this. (If (s)he does, let me know and I'll show you how to alter the calculation.)

-Dan