Hi. Welcome to the forums. I am not sure it is possible to restore the data from any app you delete from your iPad unless it saves to the cloud somewhere, or you have a backup on your computer. Because the first option is not possible, you may want to go into your computer and try to restore your iPad from a backup. This is one of those situations in which backups, Time Machine backups, and other redundancies come in handy. I have tried to restore from the previous backup. I can see the notebooks with the number of pages. but when I open them, they are empty.