Exploding Kittens- Slap to get out of multiple turns
You have been slapped thrice, so you now have 3 turns to complete.
If you have a slap card as return, you can shift all to another player. But if you don't have a slap card, you can not return.
But if you draw a slap card in an other turn, you can transfer all the remaining turns to another player. see The rules.

Double slap
End your turn without drawing a card and force any other  player to
take 2 turns in a row. This is not the same as drawing 2 cards in a
row! The target of this card should take their first turn (play cards
and/or draw). When their turn is over, it’s their turn again. If the
targeted player plays a Slap Card in return, they pick a player to
take ALL remaining turns (4 turns, then 6, and  so on). Play always
continues from the targeted player. If you draw and defuse an
Exploding Kitten during a series  of turns, you must continue taking
your remaining turns.

Example
You are targetted with a tripple slap and you have no slap to return. So you are forced to take the turn(s).

Turn 1, you draw a slap. You now have 2 turns to complete.
Turn 2, you play the slap. You target another player that gets the 2 turns of the card + your remaining turns (2nd and 3rd) for a total of 4.