I have 100 scenes, each scene has a camera, but I want only the camera from scene 1 to exist in each scene that I appear in.

I use the function DontDestroyOnLoad() to make the camera exist in each scene but I always find my self with another camera that I don't want.

Any ideas? thank you in advance.

Any one?

Nevermind -- I cannot read today.

You need to add a delegate to the SceneManager to tell you when scenes have loaded. You can then run code which removes the excess cameras.
https://docs.unity3d.com/ScriptReference/SceneManagement.SceneManager-sceneLoaded.html
Something like this:

using UnityEngine.SceneManagement;

// Put this in a monobehavior on your main camera
void OnEnable() {
    SceneManager.sceneLoaded += OnSceneLoaded;
}

// Put this in a monobehavior on your main camera
void OnDisable() {
    SceneManager.sceneLoaded -= OnSceneLoaded;
}

// Untested, but you get the idea
private void OnSceneLoaded(Scene scene, LoadSceneMode mode) {
    // Remove all cameras except this one
    foreach (Camera c in Camera.allCameras) {
    if (c.gameObject != this.gameObject) {
         Destroy(c);
    }
}

Are the other camera's there for testing?

You could give your scene one camera a tag, then write a script for the other camera's that destroy's themself on start if they find a object with that tag, but tbh Kylotans answer is way more eloquent. :rolleyes: