If your iPad is showing a message “iPad not Backed Up” the first thing you should do is restart it by pressing the Hold and Sleep/Wake buttons at the same time until the red slider shows up, then slide your finger across the slider to turn your iPad off. After turning iPad off, turn it back on by pressing the Hold and Sleep/Wake buttons down at the same time again until the Apple logo appears.
If restarting your iPad doesn’t work to clear the “iPad not Backed Up” message, restore it by connecting to iTunes. Do this by connecting your iPad to your computer, finding it under devices in iTunes, and choosing Restore. You can then backup any data from your most recent backup to iClouds or iTunes and that should fix the problem.