Faults with Grid-Based movement...

I have a few uncertainties here. I basically achieved the basics of moving the object by 1 when one of the directional keys are pressed, and it works fine. However, I also wanted the "Q" (left) and "E" (right) keys to rotate the object 90° to their direction. This is my script, I was unsure how to do the rotation, even after an hour on the Unity Script Reference.

 using UnityEngine;
 using System.Collections;
 
 public class movement : MonoBehaviour {
     public float speed = 2.0f;
     
     private Vector3 endpos;
     private bool moving = false;
     
     void Start () {
         endpos  = transform.position;
     }
     
     void Update () {
         if (moving && (transform.position == endpos))
             moving = false;
         
         if(!moving && Input.GetKey(KeyCode.W)){
             moving = true;
             endpos = transform.position + Vector3.forward;
         }
         
         if(!moving && Input.GetKey(KeyCode.A)){
             moving = true;
             endpos = transform.position + Vector3.left;
         }
         
         if(!moving && Input.GetKey(KeyCode.S)){
             moving = true;
             endpos = transform.position + Vector3.back;
         }
         
         if(!moving && Input.GetKey(KeyCode.D)){
             moving = true;
             endpos = transform.position + Vector3.right;
         }
         
         if(!moving && Input.GetKey(KeyCode.Q)){
             moving = true;
             endpos = UNSURE WHAT TO PLACE HERE;
         }
         
         if(!moving && Input.GetKey(KeyCode.E)){
             moving = true;
             endpos = UNSURE WHAT TO PLACE HERE;
         }
         
         transform.position = Vector3.MoveTowards(transform.position, endpos, Time.deltaTime * speed);
     }
 }

Thanks in advance! :D