Hi,
as far as I can tell, a direct transfer of your entries/projects from OF to NB on your iPad is not possible, copy and paste would be the only option.
If you have OF on your Mac, there is a relatively simple option, although OF does not format the result very reliably. Basically, you export your info from OF as plain text, make sure that the tasks are separated by newlines, import that document into Notebooks and select "Convert to Task List" (you can convert that list into a book)
Step by step:
1) Export your info from OF as plain text. The resulting document contains all tasks, and each task starts with a "-".
2) OF does not make sure that each tasks starts at its own line, so you should open the plain text file, make sure that each task starts at a new line and that tasks do not contain any empty lines (Notebooks interprets empty lines as delimiter between tasks)
3) You should now have a plain text file with each task starting with "-" on a new line, and empty lines separating the tasks
4) Import this file into Notebooks
5) Open the document and select "Convert to Task List"-> "Split by Paragraph"
6) If you want to use the imported info as documents rather than tasks, open the new task list's info and turn off "Show as Task List"