How to configure the range of a vector 3?

I’m trying to change the spawn area to fit the camera.

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

public class EnemySpawner : MonoBehaviour
{
    [SerializeField]
    private GameObject swarmerPrefab;
    [SerializeField]
    private GameObject bigSwarmerPrefab;
    [SerializeField]
    private GameObject flashPrefab;
    [SerializeField]
    private GameObject tankPrefab;

    [SerializeField]
    private float swarmerInterval = 3.5f;
    [SerializeField]
    private float bigSwarmerInterval = 10f;
    [SerializeField]
    private float flashInterval = 5f;
    [SerializeField]
    private float tankInterval = 10f;

    // Start is called before the first frame update
    void Start()
    {
        StartCoroutine(spawnEnemy(swarmerInterval, swarmerPrefab));
        StartCoroutine(spawnEnemy(bigSwarmerInterval, bigSwarmerPrefab));
        StartCoroutine(spawnEnemy(flashInterval, flashPrefab));
        StartCoroutine(spawnEnemy(tankInterval, tankPrefab));
    }

    private IEnumerator spawnEnemy(float interval, GameObject enemy)
    {
        yield return new WaitForSeconds(interval);
        GameObject newEnemy = Instantiate(enemy, new Vector3(Random.Range(-5f, 5), Random.Range(-6f, 6f), 0), Quaternion.identity);
        StartCoroutine(spawnEnemy(interval, enemy));
    }
}