How to change variables inside FindGameObjectsWithTag objects

so i am instantiating bombs in different location and set their tag to "Bomb" and i want when the player scores more the speed of the bombs will increase so i made a switch statement in which i put the cases of the score and tried to change the speed of the gameobjects that has the tag "Bomb" i couldnt so i stored those bombs in gameobject array and tried again and i couldn't so i made an array of speed and made a for function in which i can assign to each gameobject a speed but unfortunatly i couldnt either and the last error was :

IndexOutOfRangeException: Array index is out of range. UIMANAGEMENT.Update () (at Assets/Scripts/UIMANAGEMENT.cs:33)

i made an if statement to detect if the bombs exists in the scene then start the for function but again i couldnt

so please help me make the bombspeed changes when the player scores higher score and thank you very much

here is my code:

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

public class UIMANAGEMENT : MonoBehaviour { public Text Paused;
public Text Score; public int[] BombSpeed; public bool right; public GameObject[] explosion; public bool left; public float PlayerScore;

 void Start(){
     
 }

 public void Pause(){
     if (Time.timeScale == 1) {
         Time.timeScale = 0;
         Paused.text = "Game Paused !";
     } else if (Time.timeScale == 0) {
         Time.timeScale = 1;
         Paused.text = "";
     }
 }

 void Update(){
     explosion = GameObject.FindGameObjectsWithTag ("Bomb");
     if (GameObject.FindWithTag ("Bomb")) {
         for (int i = 0; i <= explosion.Length; i++) {
             BombSpeed [i] = explosion [i].GetComponent<Explosion> ().speed;
             switch ((int)PlayerScore) {
             case 0:
                 BombSpeed [i] = 3;
                 break;
             case 100:
                 BombSpeed [i] = 4;
                 break;
             case 300:
                 BombSpeed [i] = 6;
                 break;
             case 1000:
                 BombSpeed [i] = 8;
                 break;
             case 1500:
                 BombSpeed [i] = 10;
                 break;
             case 3000:
                 BombSpeed [i] = 12;
                 break;
             case 5000:
                 BombSpeed [i] = 15;
                 break;
             default:
                 break;
             }
         }
     }
     PlayerScore += 13 * Time.deltaTime;
     Score.text = "Score: " + PlayerScore.ToString("0");

} }