How do I restore my Audible books into iTunes? I had to do a factory restore on my laptop to Win 7 and they're no longer there.

I had to do a factory restore to Windows 7 on my HP Laptop after upgrading it to Windows 10 (due to corrupted files & Microsoft's recommendation to go back to Win 7, but then it wouldn't open anymore!). I had to reinstall all my pertinent programs including iTunes. However, my purchased Audible audio books are no longer found in iTunes. How do I get these audiobooks restored into iTunes, since they were downloaded there when I bought them?