How to get the ground position near the gameObject clicked?

Hello.

I have the Player prefab, which have some movement controls, in the RTS Style. Something really close the diablo 3. The mobs prefabs are clickable. So, when the player click the mob, it "starts" the attack. The Player has the "attackRange" to define the distance which the player are able to hit the mob. When the player is too far away from the mob (distante > attackRange), the player needs to get closer to the mob, and thats been my difficult. Here is what im doing. Any help would be appreciate!

Sorry for bad english.

 void DefineOponent(Vector3 click)
     {
         RaycastHit hit;
         Ray ray = Camera.main.ScreenPointToRay (click);
         
         if (Physics.Raycast (ray, out hit, 1000)) 
         {
             if(hit.collider.tag == "Mob")
             {
                 Oponent = hit.collider.gameObject;
 
                 if (Physics.Raycast (ray, out hit, 1000)) 
                 {
                     posicaoDestino = new Vector3 (hit.point.x, hit.point.y, hit.point.z);
                 }
             }
         }
     }

then, i do the move:

 CharacterController jogController = this.GetComponent<CharacterController>();
 this.transform.LookAt(Oponent.transform);
 jogController.SimpleMove(6 * this.transform.forward);