How to restore OneNote?

To restore notes in OneNote from a backup, you can do the following:

Select File > Info > Open Backups
Double-click the notebook folder you want to restore
Select the notebook section you want to restore and click Open
Right-click the section tab or page tabs you want to restore
Select Move or Copy
In the Move or Copy dialog box, select the destination notebook and click Copy
Right-click the backed-up section and click Close
Select your original notebook from the Notebooks list

You can also restore deleted notes using the OneNote Recycle Bin. Deleted notes are permanently deleted after 60 days.