How to make prefab clones selectable?

Edit: In players hand, for every card in it, I create a Box Collider as a component of that specific card clone game object. But I can't reach the cards seperately with OnMouseDown().

For a card game, I have a card prefab and I create clones of it after starting the game. In the players hand, I want these card clones to be selectable. How can I do this?

The function I use for the cards to be seen after adding them to the hand is:

  void AddCard(Vector3 position, int i, int cardCount) {
     if (fetchedCards.ContainsKey(i)) return;
     GameObject cardCopy = (GameObject)Instantiate (cardPrefab);
     cardCopy.transform.position = position;
     CardModel cardModel = cardCopy.GetComponent<CardModel>();
     cardModel.cardIndex = i;
     }