How to Stop Transform.Position in X-axis = 0 ?

Excuse me, anyone know how to stop my gameObject Transform.Position if x-axis = 0 ? On this case, i'll make AR with Vuforia ImageTarget, and i want to stop this transform.position in the center of imageTargets...

This is my sample code i used :

     private TrackableBehaviour mTrackableBehaviour;
     private bool isRendered = false;
     private GameObject Mobil;
     
     void Start()
     {
         Mobil = GameObject.Find("Mobil");
         
         mTrackableBehaviour = GetComponent<TrackableBehaviour>();
         if (mTrackableBehaviour)
         {
             mTrackableBehaviour.RegisterTrackableEventHandler(this);
         }
         
         OnTrackingLost();
     }
     
     void Update()
     {
         if (isRendered && Mobil.transform.position.x < 140){
         Mobil.transform.position += Mobil.transform.forward * 10.0f * Time.deltaTime;
         }
     }