Hotel Transylvania: Scary-Tale Adventures

There are three cards hidden in chests in each level. All are easy to spot and the key will be close by.

You also need to buy all the cards from the vending machines found in the hub for both the Cave of Treasures story, and the Little Red Riding... Boo story. The cards vary in price but the total coins needed is well below the total available coins.

The A Present Not Seen story doesn't have a hub but the vending machine can be found at various points while playing the levels themselves.

You will also need to visit Frank for a card in each of the two hubs after collecting all if his body parts in the associated story.

Cave of Treasures - Frank is in front of a tent to the left of the spawn.
Little Red Riding... Boo - Frank is in front of the cemetery wall as you approach the Granny's House portal.

I collected the Frank cards last but the achievement didn't pop until I had completed another level.

You can see the cards you have collected and where any you still need are located from the main menu.