Electric Fields Question - Physics A2 Level

A proton of mass 1.7x10^-27kg is moving to the right at a speed of 4.2x10^5 ms^1. It enters an electric field of 45kNC^-1 pointing to the left.
How far will the proton travel before it comes momentarily to rest?

I'm so confuseddd
E=F/Q
E=V/d

In this question, and the other one you just posted, the method is the same.

Find the force on the particle from F=Eq (you are given E and q is the proton charge.)

Then to find acceleration use F=ma (you are given m and just found F)

The distance is found from a suitable suvat equation to find s. You know a, u and also v= 0 if it stops.