How to make AI look at player

I made an AI that goes towards gameobject with tag "player", i wanted to make so he could tourn towards the player, i tried using the function transform.LookAt(), but it gives me an error, maybe because im using it in the wrong way. Can anyone help?

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

 public class EnemyRun : StateMachineBehaviour

 public float speed = 2.5f;
 public float attackRange = 3f;
 Transform player;
 Rigidbody rb;

 override public void OnStateEnter(Animator animator, AnimatorStateInfo stateInfo, int layerIndex)
 {
     player = GameObject.FindGameObjectWithTag("Player").transform;
     rb = animator.GetComponent<Rigidbody>();
 }


 override public void OnStateUpdate(Animator animator, AnimatorStateInfo stateInfo, int layerIndex)
 {
     Vector3 target = new Vector3(player.position.x, rb.position.y, player.position.z);
     Vector3 newPos = Vector3.MoveTowards(rb.position, target, speed * Time.fixedDeltaTime);
     rb.MovePosition(newPos);

     if (Vector3.Distance(player.position, rb.position) <= attackRange)
     {
         animator.SetTrigger("Attack");
     }
 }


 override public void OnStateExit(Animator animator, AnimatorStateInfo stateInfo, int layerIndex)
 {
     animator.ResetTrigger("Attack");
 }

}