Unity3D Shooter - How to switch to next level after all enemies get destroyed?

I am a newbie to Unity and I am trying to build a little shooter 2d game in C#. I am now stuck and confess that I am a little lost not knowing what the best approach is, but the problem is that my hero shoots at the enemies and they die but how do I get to the next level after the enemies are all dead? If I make a dead counter, what script do I put in? In the enemy script? Or do I make a new script but associate it with what? I also need the game to end if the hero fires his six bullets (already have a counter that makes the hero not shoot anymore after six shoots) and there are still enemies left ... Does anyone give me some tips? Thanks!

Enemy script:

   using System.Collections;
   using System.Collections.Generic;
   using UnityEngine;
 
   public class BadguyScript : MonoBehaviour
   {
       public int maxHealth;
       public int curHealth;
       private Animator myAnimator;
       private bool isDead;
       [SerializeField]
       private float DespawnTime = 2.5f;
       [SerializeField]
       private string DeathAnimHash = "isDead"; 
 
       void Start()
       {
           myAnimator = GetComponent<Animator>();
           myAnimator.enabled =true;
           myAnimator.SetBool (DeathAnimHash ,isDead);
 
 
           maxHealth = 1;
           curHealth = maxHealth;
 
       }
       void Update()
       {
           if (curHealth < 1)
           {
               isDead = true;
               myAnimator.SetBool (DeathAnimHash ,isDead);
               Destroy(gameObject,DespawnTime);
           }
       }
       void OnTriggerEnter2D(Collider2D col)
       {
           if (isDead)
              return;
           if (col.tag == "bullet")
           {
               curHealth -= 1;
               Destroy(col.gameObject);
           }
       }
   }

Count Bullets Script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class GameFlow : MonoBehaviour
 {
 
     public static float remainingShots = 6;
     public Transform shot1;
     public Transform shot2;
     public Transform shot3;
     public Transform shot4;
     public Transform shot5;
     public Transform shot6;
 
     // Start is called before the first frame update
     void Start()
     {
 
     }
 
     // Update is called once per frame
     void Update()
     {
       if (remainingShots > 0)
       {
         shot1.GetComponent<Image> ().enabled = true;
       }
       else
       {
         shot1.GetComponent<Image> ().enabled = false;
       }
 
       if (remainingShots > 1)
       {
         shot2.GetComponent<Image> ().enabled = true;
       }
       else
       {
         shot2.GetComponent<Image> ().enabled = false;
       }
 
       if (remainingShots > 2)
       {
         shot3.GetComponent<Image> ().enabled = true;
       }
       else
       {
         shot3.GetComponent<Image> ().enabled = false;
       }
 
       if (remainingShots > 3)
       {
         shot4.GetComponent<Image> ().enabled = true;
       }
       else
       {
         shot4.GetComponent<Image> ().enabled = false;
       }
 
       if (remainingShots > 4)
       {
         shot5.GetComponent<Image> ().enabled = true;
       }
       else
       {
         shot5.GetComponent<Image> ().enabled = false;
       }
 
       if (remainingShots > 5)
       {
         shot6.GetComponent<Image> ().enabled = true;
       }
       else
       {
         shot6.GetComponent<Image> ().enabled = false;
       }
 
 
       if(Input.GetButtonDown("Fire1"))
       {
       remainingShots -= 1;
       }
     }
 }