How do I add music code to my C# without getting a API update prompt?

First and foremost, the reason why I don’t want the API update is because last time I did that it completely ruined the scripts in my game and this is even after changing them back to normal and trying to get the game working.

if you want more details, read my other question: Updating the API in Unity destroyed my scripts, how do I reverse it? - Questions & Answers - Unity Discussions

So clearly I want to avoid getting this prompt again:

This is what I’m trying to do:

But every code I try I’m hit with the same prompt and I need a functioning pause menu for my game but I do need my NPC to play it’s theme when the player gets close enough.

So in short: How do I stop this prompt from happening WITHOUT doing the update?

If you’re not interested in updating your API, Unity cannot garantee that it will still work. Why are you switching Unity versions if what you have works? Do you need a new feature?
To try answering your question. Since Unity Version “I dont know” there’s a version txt file in the ProjectSettings folder of your project. If you change the Unity version to the latest, you won’t be bothered.