Moving object with touch input and detecting collision

i am making a game where player moves a cube with finger on android through 2d maze.i can move he cube,but how to check for collision with walls and obstacles which are cubes??

 Scripts:
 
 Gamescript:
 
 using System.Collections.Generic;
 using UnityEngine;
 
 public class GameScript : MonoBehaviour
 {
 
     private Dictionary<int, GameObject> trails = new Dictionary<int, GameObject>();
     private Touch pinchFinger1, pinchFinger2;
     private ParticleSystem vortex;
     
     void Update()
     {
             
     
                 // Look for all fingers
     for (int i = 0; i < Input.touchCount; i++) {
         Touch touch = Input.GetTouch (i);
             // -- Drag
         // ------------------------------------------------
         if (touch.phase == TouchPhase.Began) {
             // Store this new value
         if (trails.ContainsKey (i) == false) {
         Vector3 position = Camera.main.ScreenToWorldPoint (touch.position);
         position.z = 0; // Make sure the trail is visible
                             
         GameObject trail = SpecialEffectsScript.MakeTrail (position);
                             
         if (trail != null) {
         Debug.Log (trail);
         trails.Add (i, trail);
                 }
             }
         } 
             else if (touch.phase == TouchPhase.Moved) {
             // Move the trail
         if (trails.ContainsKey (i)) {
         GameObject trail = trails [i];
                             
         Camera.main.ScreenToWorldPoint (touch.position);
         Vector3 position = Camera.main.ScreenToWorldPoint (touch.position);
         position.z = 0; // Make sure the trail is visible
                             
         trail.transform.position = position;
             
         } else if (touch.phase == TouchPhase.Ended) {
         // Clear known trails
         if (trails.ContainsKey (i)) {
         GameObject trail = trails [i];
             // Let the trail fade out
         Destroy (trail, trail.GetComponent<TrailRenderer> ().time);
         trails.Remove (i);
                 }
             }
         }
             
         }
         }
         }
 
        

SpecialEffectsScript

using UnityEngine;

/// /// Helper class to handle particles effects /// public class SpecialEffectsScript : MonoBehaviour { private static SpecialEffectsScript instance;

 // Prefabs
 public ParticleSystem explosionEffect, vortexEffect;
 public GameObject trailPrefab;
 
 void Awake()
 {
     instance = this;
 }
 
 void Start()
 {

     if (trailPrefab == null)
         Debug.LogError("Missing Trail Prefab!");
 }

public static GameObject MakeTrail(Vector3 position) { if (instance == null) { Debug.LogError("There is no SpecialEffectsScript in the scene!"); return null; }

     GameObject trail = Instantiate(instance.trailPrefab) as GameObject;
     trail.transform.position = position;
     
     return trail;
 }

}