Help finding Average in Data Set

Hi,

I need help finding the average of a large data set. Attached is a sample. I'd like to find the average amount of Sales for Store 1, Store 2, Store 3, and Store 4. I know I can simply use the AVG equation, but the actual data set contain hundreds of stores.

Can anyone help me build a formula that will take the average amount per store?

Thanks for the help!

-Andy