Moving +1 in the x position

I am wanting to make a cube move 1 in the x position.
I’ve tried a couple of things but none have worked.
If you know how to do this, please tell me below, Thanks.

Thanks, just what I needed.
I am wanting it to be less jumpy so it doesn’t just go right to the new position, but instead slide to it.
I am thinking of adding an animation that goes with it, but please tell me if there is a better way.

rb.addForce(transform.forward * speed);
where speed is a public variable. You can also write - rb.addForce(1,0,0,speed); - in place of transform.forward if the body moves on z-axis in place of x-axis.

If you want it to stop just do this

 private Rigidbody rb;

 public float speed = 5;

 // Use this for initialization
 void Start () {
     rb = GetComponent<Rigidbody>();

 // Update is called once per frame
 void FixedUpdate () {

     if (Input.GetKeyDown(KeyCode.W)) 
         rb.AddForce(transform.forward * speed);

     if (Input.GetKeyDown(KeyCode.S)) 
         rb.AddForce(transform.forward * -speed);