How to change scenes based on an if else statement C#

I’m making a rhythm game using a list, and when the tracker hits the location of, say, 3 it spawns a note on the third string. I would like to make it so that when noteMark == 72, the scene changes to (2). Unfortunately, I’m a beginner so I don’t know how to make this work (have tried many times with if else statements, and javascript but i couldnt link it to the c# variable). Could somebody help me out? I’ll put in the code for reference. When you answer, please also advise me WHERE to put it in the code.

public class gm : MonoBehaviour
{
	List<float> whichNote = new List  <float>() { 1, 6, 3, 4, 2, 5, 2, 1, 2, 3, 5, 6, 4, 6, 5, 5, 1, 2, 4, 1, 1, 4, 5, 1, 3, 2, 5, 1, 6, 4, 5, 3, 1, 2, 2, 5, 6, 2, 4, 5, 4, 1, 6, 2, 4, 3, 5, 1, 5, 4, 3, 6, 3, 2, 4, 5, 6, 4, 1, 1, 6, 2, 3, 6, 1, 6, 2, 5, 4, 1, 3, 2, 2,};
	//creates a list of values which can be called based on their position

	public int noteMark = 0;
	//tracks position of note, starting at 0

	public Transform noteObj;
	//variable storing the prefab of the note

	public string timerReset = "y";

	public float xPos;
	//the X position of where the note will be spawned (decides which of 5 rows it'll go down)

	public static int winStreak = 0;
	//variable for how many consecutive notes you get right

	public static float totalScore = 0;
	//variable for score

	public Transform fountainfw;
	//variable storing the prefab of the fireworks
	public string fountainSpawnL = "n";
	//variable checking whether the left fountain has been spawned
	public string fountainSpawnR = "n";
	//variable checking whether the right fountain has been spawned

	// Use this for initialization
	void Start()
	{

	}

	// Update is called once per frame
	void Update()
	{
		if ((timerReset == "y") && (noteMark<72))
		{
			StartCoroutine(spawnNote());
			//runs the IEnumerator code
			timerReset = "n";
			//so the notes don't spawn on top of each other every frame, timer is reset to give it enough time
		}

		if ((winStreak == 5) && (fountainSpawnL == "n"))
		{
			fountainSpawnL = "y";
			Instantiate(fountainfw, new Vector3(2.35f, 1.32f, 0.59f), fountainfw.rotation);
			//when winstreak is 5, first sparkle fountains comes up
		}
		if ((winStreak == 10) && (fountainSpawnR == "n"))
		{
			fountainSpawnR = "y";
			Instantiate(fountainfw, new Vector3(-2.33f, 1.32f, 0.59f), fountainfw.rotation);
			//when winstreak is 5, second sparkle fountain comes up

		}
	}
	IEnumerator spawnNote()
	{
		yield return new WaitForSeconds (0.7f);
		//it waits 0.65 seconds, then spawns the note

		if (whichNote [noteMark] == 1) {
			xPos = -1.35f;
		}
		//When the note reads value 1 on the list it spawns a note on the last string
		if (whichNote [noteMark] == 2) {
			xPos = -0.8f;
		}
		//When the note reads value 2 on the list it spawns a note on the second last string (and so on)
		if (whichNote [noteMark] == 3) {
			xPos = -0.3f;
		}
		if (whichNote [noteMark] == 4) {
			xPos = 0.35f;
		}
		if (whichNote [noteMark] == 5) {
			xPos = 0.9f;
		}
		if (whichNote [noteMark] == 6) {
			xPos = 1.3f;
		}
		noteMark += 1;
		//Moves the position of the next note
		timerReset = "y";
		Instantiate (noteObj, new Vector3 (xPos, 2.15f, -3), noteObj.rotation);
		//adds these when the program starts; the note object, the top of guitar, an the rotation of the note object

	}
}

if (noteMark == 72)
{
SceneManager.LoadScene(2);
}

Just add this someplace you want.