vector 3 to unity.transform

using UnityEngine; using System.Collections;

public class PatrolUpstairs : MonoBehaviour {

 public Transform[] points;
 private int destPoint = 1;
 private UnityEngine.AI.NavMeshAgent agent;
 public float range = 10f;
 public float stop = 2f;
 public float move_speed = 3f;
 public float turn_speed = 4f;
 public Transform player;
 Transform myTransform;

 void Start () {
     player = GameObject.FindWithTag ("Player").transform;
     agent = GetComponent<UnityEngine.AI.NavMeshAgent>();
     myTransform = transform;

     // Disabling auto-braking allows for continuous movement
     // between points (ie, the agent doesn't slow down as it
     // approaches a destination point).
     agent.autoBraking = false;

     GotoNextPoint();
 }


 void GotoNextPoint() {
     // Returns if no points have been set up
     if (points.Length == 0)
         return;

     // Set the agent to go to the currently selected destination.
     agent.destination = points[destPoint].position;

     // Choose the next point in the array as the destination,
     // cycling to the start if necessary.
     destPoint = (destPoint + Random.Range(1,(10))) % points.Length;
 }


 void Update () {
     // Choose the next destination point when the agent gets
     // close to the current one.
     float distance = (myTransform.position - player.position).magnitude ;
     if (distance <= range)
         myTransform.rotation = Quaternion.Slerp (myTransform.rotation,
             Quaternion.LookRotation (player.position - myTransform.position), turn_speed * Time.deltaTime);
     if (distance > stop)
         agent.destination = player;

     if (agent.remainingDistance < 1f)
         GotoNextPoint();
 }

}

My error is: Cannot implicitly convert type UnityEngine.Transform' to UnityEngine.Vector3'

How can I measure the distance between two gameobjects without using vector 3?