Excel date conversion and pivot table

Hi, need to learn how to do the following. 1. mass convert column D from unrecognizable to recognizable date for formula on column F to work. Column D is currently formatted to display date but it becomes active only when I double click inside cell and hit enter. I need to learn how to do this date covertion in mass for entire column D. Good example of what I need is Column D1 thru D6. I need to be able to make this date conversion in mass. 2. Create Pivot table that can sum Part Numbers Pieces but grouped or separated by date. Example: Part Number 33109001 has 21 line items totaling 1050 pieces, I need it to show 1 line item with 1050 total pieces and grouped or separated by date. Objective is to sum Part Number Pieces (column B) by Part Number and group by date as to visualize age of sum of entire part numbers. I'm only supplying a small set of the data for your review.