Where do Fortnite Exclusive sites get their codes from?

My name is Louis, and I wanted to ask if you know where the Fortnite Exclusive sites get their codes from, such as eneba.com → because such sites legally sell codes for games, in-game currencies such as dances, coins / V- Bucks / Skins etc.

But where do they get the codes from? Because at eneba.com you can buy the "Bhangra Boogie" emote for around 7 euro, although you actually need a cell phone for around 500+ euro?! (One Plus)

It would be nice if you could answer this question for me.

They have large suppliers who get them from any database. But where exactly they get all the codes is not traceable for customers