This warning is telling you that your server has been modified away from what Atlassian distribute and support
It is not an error, it is just trying to tell you that the changes you have made on the server could be destroyed by the upgrade, so you might want to look at why you made them and think about re-doing them if you need to after upgrade.
Yes, it will. You have modified some of the installation, and it is telling you about it so you know you have to think through re-applying the changes to the upgraded version.
I'm not sure why you started to talk about migration.
Edit - sorry, I should have said this sooner:
The three files it is warning you about are not a huge worry.
The third one is a database driver that you actually need for running the system. It should stay in place during an upgrade.
The second one is a properties file you've added, presumably for configuring some extra logging. I doubt this will be anything to worry about, as I don't think log4j has changed the way it is configured.
The first is the difficult one - it's a batch file, used by Windows when you are running confluence as a service. The upgrade may put this file back, so you'll need to think about why you deleted it before in case you have a reason to delete it again.
Hi Community! We're thrilled to share that Team Calendars for Confluence is now a built-in feature for Confluence Data Center releases 7.11 and beyond. A long time favorite, Team Cale...
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events