Inventory PAR Levels

I am working on inventory PAR level project. I have data from the last 3 months and need to determine what the PAR levels should be to ensure that there is never shortage or an overstocking issue. I have the data from all 3 months on one worksheet but want to be able to place on another worksheet the PAR levels for each of the products. Attached is a sample data set. Can someone help - PLEASE!!