Hello,
We would like to know more about the activation issue you're experiencing with the N edition of Windows 10. Have you tried running the Activation troubleshooter? If not, kindly follow the steps outlined in this support article.
Once activated, you can perform the upgrade to Windows 10 Pro using Easy Upgrade. Andre Da Costa provided a link in his article on how to perform this operation. This procedure will preserve your personal data, apps, and personal settings. Easy Upgrade will only be available on a system that is properly activated.
If you're worried about your personal files, you can check this article on how to manually back up and restore files in Windows 10.
Let us know if you have other concerns about Windows 10.