Can't find audiobooks in Itunes

Hi,

I use Itune 12.4.3.1 on Windows 10.

I have a good numbers of audiobooks. A lot of them are homemade mp3 files. I dont't have a lot a audiobook from the applestore.

I uses tihs for several years. But, now I can't find my book. My book folder is empty.

When I go to the itunes folder on explorer my entire library is tthere.

Thank for the help,