What is the expiation for someone who, as a child, stole cosmetic tools from the World Assembly of Muslim Youth due to ignorance and lack of awareness?

A child is not held accountable, from a religious perspective, before reaching puberty. However, he must guarantee what he has damaged or stolen from people's property and rights. If the stolen item exists, he should return it; otherwise, he is liable for its value on the day it was stolen, unless the owner of the right absolves him.