How can you get a code from pet pet park that has no been redeemed yet

That's easy! You just have to look at the code card things(if you're looking for NC),
then you look at the selected stores. Then you ask you're parents when you can go and when you go there, be sure to look for the NC card. But if you're looking for a different kind of code, good luck about finding that. All I know is how to get a NC card.