How to make a if then statement for button

So I made a game off of roll a ball and I’m trying to modify it to have more levels. I made a first scene that is my fist level once you win that first level I have a “you win” text that pops up. I need to figure out a script that allows me to pop up a button after the text pops up to allow me to go to my next level witch is the next scene. Please give me some help on how to make a pop up button. I know the scripting for using that button to get to the next scene but not how to make that button pop up. I am using C# for all of my scripting.

using UnityEngine.UI; // put this at the beginning to reference UI stuff

public Button nextBtn; // make a reference to a button and assign it in the editor

nextBtn.gameObject.SetActive (true); // deactivate the object in the editor, activate it when you need it