Thank you for using JustAnswer.com my name is Josh and I am going to assist you today
When a file is deleted from the notepad they are removed and can only be recovered by a backup (if one was completed or setup) or by using third party software to look for the data.
From your description of the deleted files it sounds like no backups are avalible
So the next thing to try is third party software that can scan your device and see if it can locate the deleted files on the memory chip in your notepad
An online guide and download can be found here:
Another option is:
And an app that runs directly on your notepad
If third party software can not locate the deleted files then they have been removed permanently