dose anyone know how to sell your pokemon for credit for cards?

Most card game stores will buy cards for cash or store credit. They usually give you more in credit, so that is a better option if you want to buy more cards with the money and support your LGS.

You could also try selling them online on sites like eBay, or specialised card sites like TCGPlayer. The disadvantage being that you have to list, package and ship the cards to individual buyers yourself, and there is a risk of being scammed, but you can make more money than stores offer if you know what you are doing and put the time into it.

I don't know how old you are, but if you are too young to have your own bank account, you might need your parent's help selling cards online. Not to mention their permission to sell them online in the first place.