So I made my starter edition account loved the game. But can I buy my expansion pack in stores or do only have to buy it online.if I have to buy it online how do I buy it in stores.
You can either buy it on stores or online.
For stores, just go to a brick and mortar store and see if they have Warlords of Draenor (the latest expansion, it contains all previous expansions)
You can buy the physical box from amazon as well.
But! I highly suggest you buy it directly from Blizzard at http://us.battle.net/wow/en/shop/
it will come with 1 month of subscription and then you have to either buy more gaming time in a store in the form of a time card, or with Battlenet balance, or just register a valid credit card.
After that you are good to go, the Base already has the complete game downloaded. You can continue with your character wherever you left off, and venture in the world of warcraft.