public class ReplicateMesh : MonoBehaviour
{
    public int rows;
    public int columns;
    public GameObject meshPrefab;

    public void Start()
    {
        if (meshPrefab == null)
            return;

        for (int rowIndex=0; rowIndex < rows; rowIndex++)
            for (int colIndex = 0; colIndex < columns; colIndex++)
                Instantiate(meshPrefab, new Vector3(rowIndex - rows/2f, 0, colIndex - columns/2f), Quaternion.identity, this.transform);
    }
}