What is the name of the backup file and where is it located in Windows 10?
Consider getting support from official wiki page of BurnSoft, the original developer.
You can check here: On Windows 10, the Backup folder for your notebooks is located at C:\Users\user name\AppData\Local\Microsoft\OneNote\version\Backup.
Another smart way you can use SysInfo free BKF file viewer which automatically detects the windows backup file from your system and open them. Its completely free of cost. Just download and view.
In C drive -> Users -> Your windows username.