I Have an C# error and I can't fix it @username

In line “block = Instantiate (Blocks [Random.Range (0, 5)], BlockSpawnPos.position, Quaternion.identity) as GameObject;” has an error @username

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class BlockSpawn : MonoBehaviour 
{
	public GameObject[] Blocks;
	public Transform BlockSpawnPos;
	public int BlockCount = 0;
	public float NewPos;

	private int randomNum;
	private float waitTime = 2.0f;



	// Use this for initialization
	void Start () 
	{
		Block();
	}
	
	// Update is called once per frame
	void Update () 
	{
		
	}
	public void Block()
	{
		block = Instantiate (Blocks [Random.Range (0, 5)], BlockSpawnPos.position, Quaternion.identity) as GameObject;
		Vector3 temp = BlockSpawnPos.position;
		temp.y = 0;
		temp.x += 5;
		temp.z = 0;
		BlockSpawnPos.position = temp;
		StartCoroutine (wait());

	}
		IEnumerator wait(){
		yield return new WaitForSeconds (waitTime);
		BlockCount += 1;
		Block ();
		}
}

block has no type.
You can use var as you assign it on the same line :

var block = Instantiate (Blocks [Random.Range (0, 5)], BlockSpawnPos.position, Quaternion.identity) as GameObject;

You can type it too

GameObject block = Instantiate (Blocks [Random.Range (0, 5)], BlockSpawnPos.position, Quaternion.identity) as GameObject;

Or, as you don’t seem to use it later, you can just discard it

Instantiate (Blocks [Random.Range (0, 5)], BlockSpawnPos.position, Quaternion.identity);