What should I indicate when asked the purchase price of hundreds of items donated when I'm not privy to that information?

I am clearing out a family member's estate and have donated hundreds of items to Goodwill throughout the year.. (Clothing, small appliances, Paintings,Tables, Lamps, Books ... just to name a few)  I received receipts from the donation attendant each time that simply noted the Donation Quantity as being a SUV load full.  Then boxes were checked on the receipt indicating clothing, furniture housewares or whatever I was donating.  I personally kept a detailed list of what I was dropping off and used Goodwill's valuation guide to determine the value of things.  I sat down to do my taxes and got to the charitable donations section and I began by listing the first date I donated and the items I gave.  After I listed this in TurboTax I then am asked for a purchase price.  I have no idea what was paid for the items, not to mention I have a list that is 4 pages long of the items I donated.  Is it necessary to list each item, it's purchase price (which I would be guessing on).