How to refer to script from another scene?

I want refer to dont destroy on load object.

If this is a single “manager” type of script, a common way is to use the Singleton Pattern, where a static variable stores a reference to the instance of the script. You can find various explanations to this online by looking up Unity Singleton.

Another approach is to use FindObjectOfType<>(), which is like get component, but searches all your GameObjects.