Is repentance sufficient after taking cards from my father's store without his knowledge, or is it necessary to inform him or compensate him for the money without his knowledge?

You must repent for taking the cards without your father's permission. The conditions for repentance are: immediately ceasing the act, resolving not to return to it, and restoring rights to their owners or seeking their forgiveness. You are not required to inform your father; rather, return the money by any means possible. Strive to determine the value of the cards and deliver the money to him.