CSHARP

unity enable gameobject

GameObject.Find("PlayMenu 3").SetActive(false);
// you could also store a GameObject as  variable

unity enable gameobject

 // Drag & Drop the gameobject in the inspector
 public GameObject targetGameObject ;

 public void DisableGameObject()
 {
      targetGameObject.SetActive( false ) ;
 }

 public void EnableGameObject()
 {
      targetGameObject.SetActive( true ) ;
 }

 public void ToggleGameObject()
 {
      if( targetGameObject.activeSelf )
           DisableGameObject() ;
      else
           EnableGameObject();
 }

on GAMEOBJECT enable unity

    void OnEnable()
    {
        Debug.Log("PrintOnEnable: script was enabled");
    }