Audio books
i upgrade to new OSI and all audio books disappeared. How can I get them back?
Do you mean that you've updated the iOS version on your device ? If you do (and if they were bought from iTunes) then in the iBooks app on the device you will need to search for each one in the store and see if they are available for redownloading : Download your past purchases - Apple Support
If they are no longer in the store, or if you've moved countries since buying them, you won't be able to redownload them - if that is the case you will have to sync them back from your computer's iTunes library / backup of your downloads/library