Kardwill: Errr... I had the same question, and I'm probably a little dense, but where?
The folders I see on the "account" page are games, wishlist, gifts, messages, settings, and I don't see any option for the store credits/fair price packages I collected.
If I recall correctly, it should appear on the top right of your account, above the "sort by" tab. Alternatively, you can check how much store credit you have by trying to buy a game and you will notice a choice to buy it with your current balance of store credit. Alternatively alternatively, a reason why you might not be seeing it, is because GOG stores two credit balances; one in € and one in $. Try changing your currency and see if your store credit appears.