Dear Guillaume AMGAR,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
As per your description, according to this article: Import notes from Evernote into OneNote 2016 for Windows - OneNote (microsoft.com)
We noticed that the importer software described on this page is still available for you to download and use, but Microsoft related teams are no longer actively developing or supporting this tool.
So, if you had followed the steps in the above article to Import notes from Evernote into OneNote 2016 and you cannot find the tool, I am afraid this may be due to the imported tool no longer support. In this case, it’s recommended to manually copy and move the notes between Evernote and OneNote apps.
Your understanding and patience will be highly appreciated. I hope that you are keeping safe and well!
Sincerely,
Waqas Muhammad