Detect if player is in range?

Trying to detect if the play is within range of the enemy for a simple AI script. It's been a while since i last coded so I am suffering memory loss lol. I tried OnCollisionEnter, OnTriggerEnter, but was having trouble remembering, Rigid body on just one? or Both? Collider on one or both? is trigger isn't trigger? is Kinematic isn't kinematic? So I thought well lets just detect distance on a Vector3 but not even that is working for me now. Here is what I have, let me know some tips, or any advice to solve this issue.

 using UnityEngine;
 using System.Collections;
 
 public class EnemyAI : MonoBehaviour {
 
     public GameObject target;
 
     public int maxRange;
     public int minRange;
     private Vector3 targetTran;
     // Use this for initialization
     void Start () 
     {
         target = GameObject.FindWithTag("Player");
         targetTran = target.transform.position;
     }
     
     // Update is called once per frame
     void Update () 
     {
         if ((Vector3.Distance(transform.position, target.transform.position) < maxRange)
            && (Vector3.Distance(transform.position, target.transform.position) > minRange))
         {
             transform.LookAt(targetTran);
             transform.Translate(Vector3.forward * Time.deltaTime);
         }
     }
 }