How would add an scene on the Countdown Timer

I need to know where I should add an scene in my Countdown Timer script . The purpose for having a scene for the player . If the player wins or lose . I also have and Score System script. Here are my scripts :

using UnityEngine; using UnityEngine.UI;

public class MyClock : MonoBehaviour { public int Minutes = 0; public int Seconds = 0;

   private Text    m_text;
   private float   m_leftTime;
  
   private void Awake()
   {
       m_text = GetComponent<Text>();
       m_leftTime = GetInitialTime();
   }
  
   private void Update()
   {
       if (m_leftTime > 0f)
       {
           //  Update countdown clock
           m_leftTime -= Time.deltaTime;
           Minutes = GetLeftMinutes();
           Seconds = GetLeftSeconds();
  
           //  Show current clock
           if (m_leftTime > 0f)
           {
               m_text.text = "Time : " + Minutes + ":" + Seconds.ToString("00");
           }
           else
           {
               //  The countdown clock has finished
               m_text.text = "Time : 0:00";
           }
       }
   }
  
   private float GetInitialTime()
   {
       return Minutes * 60f + Seconds;
   }
  
   private int GetLeftMinutes()
   {
       return Mathf.FloorToInt(m_leftTime / 60f);
   }
  
   private int GetLeftSeconds()
   {
       return Mathf.FloorToInt(m_leftTime % 60f);
   }

}

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

public class ScoreManager : MonoBehaviour { public int currentScore = 0; public Text text; ScoreManager scoreManager; void Start () {
text = GetComponent (); currentScore = 0; UpdateScore(0); scoreManager = gameObject.GetComponent(); // this may not be exactly how you get a reference to ScoreManager

  }
 
  void UpdateScore(int score)
  {
      currentScore += score;
      if (text != null)
      {
          text.text = "Score :" + currentScore;
      }
   scoreManager.UpdateScore(100);
  }

}