FLIP: Excavate cards from the top of your Deck until you excavate a Spell/Trap, then add that card to your hand, also send the remaining cards to the GY.
Rulings
Individual Card FAQs
You need to show the cards to your opponent, including the one you keep.
If you pick up your entire Deck and there were no Spell or Trap Cards, then "Magical Merchant"'s effect disappears.