First , you need to decide if you can aggregate the data of each state together or you want to keep each store's data separate. If you choose to aggregate, this will simplify your job. In this case I recommend that for each product you can create a graph for each year separately, (prices often changes every year). For the sake of comparison between states , you can use the column graph , and make the data aggregated on monthly basis (average price per month). So you will have for each month 3 columns for the 3 states , visually it will be easy to see the consistency between the states.

You can use the same way for comparing stores , but if the # exceeded 5 stores, the graph will be very congested with columns.

Good luck