Finding prefab-camera which is child of main camera

Hi i`m using unity for some college assignments

I get "Easy Fog of War" asset in unity asset store and apply it on my own unity project. It said that put a prefab camera which makes fow as the child of main camera.

my own unity project is a slightly modified version of "Minimalist Puzzle" asset. At the start of the game(at void Awake(){}), Gamemanager Scripts adjusts main camera`s orthographicsize to fit in the game scene. And it doesn`t move until that stage ends.

after applying FoW, I can`t find the way to adjust the orthographicsize of prefab camera. If I can`t find it, I can still build it and run it but those 2 camera have different orthographicsize. So it looks weird.

I want to find the prefab camera which is child of main camera inside the Gamemanager. Then, I can adjust it`s orthographicsize.

this is my hierarchy


And this is part of my script when adjusting the orthogrpahicsize of camera

private void Awake()
{
inst = this;
Camera cam = Camera.main;
//Camera cam2 = transform.Find("FowCamera");
//Set Screen Size
float orth;
if (Screen.height < Screen.width)
{
//Horizontal
Ui[0].GetComponent<GridLayoutGroup>().constraintCount = 4;
Vector2[] point = Collider.points;
point[0] = new Vector3(100, 175);
point[1] = new Vector3(-100, 175);
Collider.points = point;
Collider.transform.eulerAngles = new Vector3(0, 0, -90);
orth = Collider.bounds.size.y * Screen.height / Screen.width;
Debug.Log(orth); Debug.Log(cam);
}
else
{
orth = Collider.bounds.size.x * Screen.height / Screen.width * 0.5f;
}
Camera.main.orthographicSize = orth;
Debug.Log(Camera.main.orthographicSize);
//cam2.orthographicSize = orth;

 

Additionally, I can`t use transform.getchild() cuz it returns unityengine.transform but I need unityengine.camera to adjust orthographicsize