Customize Vector3 Inspector

I would want all the Vector3 had and horizontal view way into the inspector:

I was trying with this:

 [CustomEditor(typeof(Vector3))]
 public class Vector3Editor : Editor
 {
     void OnInspectorGUI()
     {
         target = EditorGUILayout.Vector3Field(target .name, target );
         if (GUI.changed)
             EditorUtility.SetDirty(target);
     }
 }

But the compiler doesn't let me to do it , Any idea?