Because the list view only allows one line view but there may be multiple purchases for one item the best you can do is to display the most recent purchase date of a Part in the Part list.
When selecting "Modify Table View", you need to select a field from a different table.
Above the list of available fields is a drop down menu which allows you to select a different Table. If you select "Inventory Parts Portal" from this list, a new list of available fields will show.
In this list is a field called "Part Date", this is the purchase date of the part.