How to save score in new scene??

So I have 3 scenes: menu main and over
so score in main scenes and i want over secens have value of score variable. So How i can do that?

Set Object.DontDestroyOnLoad to the component where you save the score. Take into account to put this component only in your main scene, so it doesn’t get replicated.

Also, check the Singleton Pattern, this might help you understanding this.