`SceneManager' does not contain a definition for `LoadScene'

hi, can someone please help me with this error:

Assets/Menu.cs(53,22): error CS0117: `SceneManager' does not contain a definition for `LoadScene'

here’s my script, thanks.

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
using UnityEngine.SceneManagement;

public class Menu : MonoBehaviour {

	public Canvas quitMenu;
	public Canvas instractionsMenu;
    public Button startText;
	public Button exitText;
	public Button instractionsText;

    // Use this for initialization
    void Start () 
	
	{
		quitMenu = quitMenu.GetComponent<Canvas> ();
		instractionsMenu = instractionsMenu.GetComponent<Canvas> ();
        startText = startText.GetComponent<Button> ();
		exitText = exitText.GetComponent<Button> ();
		instractionsText = instractionsText.GetComponent<Button> ();
        quitMenu.enabled = false;
		instractionsMenu.enabled = false;

    }


	public void ExitPress()

	{
		quitMenu.enabled = true;
		startText.enabled = false;
		exitText.enabled = false;
		instractionsMenu.enabled = false;
		instractionsText.enabled = false;
    }

	public void NoPress()

	{
		quitMenu.enabled = false;
		startText.enabled = true;
		exitText.enabled = true;
		instractionsMenu.enabled = false;
		instractionsText.enabled = true;

    }

	public void StartLevel()

	{
        SceneManager.LoadScene("1");
    }

	public void ExitGame()

	{
		Application.Quit ();
	}

	public void instractionsPress()

	{
		quitMenu.enabled = false;
		startText.enabled = false;
		exitText.enabled = false;
		instractionsMenu.enabled = true;
		instractionsText.enabled = false;
	}
}

Try Application.LoadLevel(n); where n is the index of your scene in build settings.