I believe that to analyse my data using pivot tables and pivot charts, my raw data must be formatted as a "list". Unfortunately it isn't. Can anyone help me to reorganise it please?

I'm analysing sales data for several products, by monthly sales over three years. The data is sent to me in the following format: the column headers are product, year, sales in Jan, sales in Feb, sales in Mar..... sales in Dec. I want a pivot chart with the product in the page field, sales figures up the side and months along the bottom, with a different line (data series) for each year. I think to do this I need to convert my data so that the columns headers are product, year, month and sales, and apply the pivot table to that.

How can I quickly transfer the sales figures in the columns "Jan sales", "Feb sales" etc so that they each appear on a separate row that states the month in one column and the sales for that month in another? Do I actually need to do it like this?

Any help gratefully received!