Where can I find the private keys for my wallet?
As Coinbase is a hosted wallet, it's not feasible to provide the private keys to individual wallet addresses; doing so would prevent us from taking advantage of our secure cold-storage technology
to protect your funds. This not only ensures your security but it also allows us to reduce the cost of sending digital currency to another Coinbase account.
You can always find and create new addresses to be associated with your Coinbase wallet on your Addresses