How to upgrade from 8.4.5 to 9.10

Dear Support & Community,
I did try to use notification application (and the watchlist linked to it) in order to receive mail notification of what is going on our Wiki.
However, even after configuring the SMTP settings with the admin rights, I did not receive any modification alert by mail.

Then, I did try to upgrade the notification application in order to fixe this problem, but I think I need to first upgrade the XWiki from 8.4.5 to 9.10.

capture 20

If I’m right, could you please explain to me how to do it ? I did install the XWiki 8.4.5 with the .exe

Thank you very much for your help.
I’m available if you want more details.

Kind regards.