[2D] Moving the player 1 tile at a time using rigidbody movement

First off, I am still quite new to this, so please be considerate if I made any idiotic mistakes. Having said that, I am trying to do little a 2D tile based RPG, however, when I started to implement colliders (to restrict the area accessible to the player), I quickly realized that the way I was moving the player around was not going to work (player was able to go through colliders if the respective movement key was being pressed repeatedly). Upon discovering this I did a bit of research and saw that you are supposed to use the physics engine (rigidbody) to move the player around, but I do not know how or if it is possible to restrict movement to one tile at a time (one per buttonpress) like this.

TL;DR Trying to do player movement using the rigidbody (physics engine) but restrict movement to one tile at a time (per buttonpress)

This is the script I am currently using. What would I need to change?