How to move Instantiated 2D objects by 0.5 using arrows

I have this block breaker type of game. Where you start the ball and then it goes bouncing around, and you have to hit it back with a paddle. Now I want to have God Mode, where user can design a level him/herself. Each block is 1x1 size and there are 4 types of blocks as you can see. I have managed to code instantiating each with different keys(1,2,3,4), but now I have trouble designing them around. They all instantiate in the middle of the screen (0,0), on top of each other, and if the user might instantiate like 200 of them, I worry, the game might lag or something. Because the screen is 16x12. Here’s my code for instantiating these prefabs, what can I do to improve and move them around, save and add next prefab and finally finish it. If they could test, it would be even better.

public GameObject block3hit;
	public GameObject block2hit;
	public GameObject block1hit;
	public GameObject unbreakableBlock;

	void Start()
	{
		
	}

	private void Update()
	{
		
		SpawnBlock3();
		SpawnBlock2();
		SpawnBlock1();
		SpawnBlock4();
	}

	void SpawnBlock3()
	{
		if (Input.GetKeyDown(KeyCode.Alpha3))
		{
			GameObject k = Instantiate(block3hit);
			k.transform.position = new Vector2(0, 0);
		}
	}

	void SpawnBlock2()
	{
		if (Input.GetKeyDown(KeyCode.Alpha2))
		{
			GameObject k = Instantiate(block2hit);
			k.transform.position = new Vector2(0, 0);
		}
	}
	void SpawnBlock1()
	{
		if (Input.GetKeyDown(KeyCode.Alpha1))
		{
			GameObject k = Instantiate(block1hit);
			k.transform.position = new Vector2(0, 0);
		}
	}
	void SpawnBlock4()
	{
		if (Input.GetKeyDown(KeyCode.Alpha4))
		{
			GameObject k = Instantiate(unbreakableBlock);
			k.transform.position = new Vector2(0, 0);
		}
	}

I dont get your post.

Are you asking hot to move objects? change its transform.position.

Do something like:

GameObject NewObject = Instantiate (blablabla)

Then change its transform.position

NewObject.transform.position += New Vector2 (0,5f, 0);