How can I spawn a prefab relative to a cube position?

Good evening everyone, I can not spawn a prefab relative to a cube position, I want to spawn the prefab in position Z+1. My Script in C# my prefab is "public GameObject seta1;"

 public class regraBlocos : MonoBehaviour {
 
  
 
 public Vector3 selfPosition;
 
 private bool blocoAtivo = true;
 
 public bool blocoPressionado = false;
 
 public GameObject seta1;
 
 public GameObject seta2;
 
 public GameObject seta3;
 
 public GameObject seta4;
 
 public Vector3 spawnSpot1;
 
 public Vector3 spawnSpot2 = new Vector3(0, 0, 0);
 
 public Vector3 spawnSpot3 = new Vector3(0, 0, 0);
 
 public Vector3 spawnSpot4 = new Vector3(0, 0, 0);
 
 private int pushing = 0;
 
 // Use this for initialization
 
 void Start () {
 
 selfPosition = transform.localPosition;
 
 }
 
 void SpawnSetas(){// regra para spawnar somente uma vez
 
 if (pushing == 0)   {
 
 Instantiate
 
  
 
 (seta1,transform.localPosition, Quaternion.identity);
 
  
 
 }
 
 pushing = 1;
 
 }
 
  
 
  
 
 // Update is called once per frame
 
 void Update()
 
  
 
 {
 
 if (Input.GetMouseButtonDown(0) & blocoAtivo ==true)
 
 {
 
  
 
 RaycastHit hitInfo = new RaycastHit();
 
 bool hit = Physics.Raycast(Camera.main.ScreenPointToRay(Input .mousePosition), out hitInfo);
 
 if (hit) 
 
 {
 
 if (hitInfo.transform.gameObject.tag == "BLOCO" & blocoAtivo ==true)
 
 {blocoPressionado = true;
 
 SpawnSetas();
 
 } 
 
 //regra se o ray colidir com as tags o bloco se move
 
 if (hitInfo.transform.gameObject.tag == "CIMA" & blocoAtivo ==true)
 
 {transform.position = new Vector3(transform.position.x, transform.position.y, transform.position.z + 1.0f);
 
 blocoAtivo = false;} 
 
 if (hitInfo.transform.gameObject.tag == "DIREITA" & blocoAtivo ==true)
 
 {transform.position = new Vector3(transform.position.x + 1.0f, transform.position.y, transform.position.z);
 
 blocoAtivo = false;} 
 
 if (hitInfo.transform.gameObject.tag == "BAIXO" & blocoAtivo ==true)
 
 {transform.position = new Vector3(transform.position.x, transform.position.y, transform.position.z - 1.0f);
 
 blocoAtivo = false;} 
 
 if (hitInfo.transform.gameObject.tag == "ESQUERDA" & blocoAtivo ==true)
 
 {transform.position = new Vector3(transform.position.x - 1.0f, transform.position.y, transform.position.z );
 
 blocoAtivo = false;} 
 
  
 
 }
 
 }
 
 }
 
 }