audio books on my iPad?

How are you trying to access them ? If you've synced them from your computer's iTunes or bought and downloaded them directly on the iPad then they should be in the Music app - when you have audiobooks on an iPad you will get an Audiobooks option under the More button at the bottom of the Music app.

If you have bought them directly on the iPad then note that audiobooks are currently a one-time only download from the store (so they won't appear in the Purchased tab in the iTunes store app for re-downloading), so you may want to copy it to your computer's iTunes via File > Devices > Transfer Purchases so that you can take a backup copy of it - it should copy over to the Books part of your iTunes library.