How to load parts of a large tilemap like chunks in Unity 2d?

Question

I use more pictures so you can understand my opinion better.
Here is the video link I recorded.

My code has a problem that I use for to render it and cause it to "lag" for 1-5 seconds, so I need to optimize it, and I found one way is to use chunks, and why I don't use the tilemap and it drops my fps

This links to my map data and my code.

// this is my function I use to create clone game object
if (Vector3.Distance(target.position, topLeft) < 25f
         || Vector3.Distance(target.position, topRight) < 25f
         || Vector3.Distance(target.position, bottomLeft) < 25f
         || Vector3.Distance(target.position, bottomRight) < 25f)
{
    // My code is currently running "fine", but when it renders the 
    // map in 1-2s it will drop fps because of the for loop, then it will increase again
    xMin = xMin - 1;
    xMax = xMax + 1;

    yMin = yMin - 1;
    yMax = yMax + 1;

    GetCircumjacent();
    for (int x = xMin; x < xMax; x++)
    {
        for (int y = yMin; y < yMax; y++)
        {
            if (x == xMin || y == yMin || x == xMax - 1 || y == yMax - 1)
            {
                try
                {
                    int mapX = xCenter + x;
                    int mapY = yCenter + y;
                    
                    // this is when I get the prefabs from the array prefabs I added
                    GameObject clone = Instantiate(prefabs[map[mapX, mapY]], this.transform);
                    clone.transform.position = zero + new Vector3(x, y);
                }
                catch (Exception e)
                {
                    Debug.Log("Error: Index out of range");
                }
            }
        }
    }
}

private void GetCircumjacent()
{
    topLeft = zero + new Vector3(xMin, yMax - 1);
    topRight = zero + new Vector3(xMax - 1, yMax - 1);

    bottomLeft = zero + new Vector3(xMin, yMin);
    bottomRight = zero + new Vector3(xMax - 1, yMin);
}