I have uninstalled the old XAMPP and deleted all of the content of d:\\xampp folder and installed the new one. When I copy my backup folder (with the name of my
I found this searching for the way to recover my XAMPP databases in Ubuntu. The question is obviously for a Windows system, but I think this might be of help since this was the only good search result.
For a standard installation in /opt/lampp/. You can recover the databases from the folder /opt/lampp/var/mysql/ if you have a backup of the whole lampp installation. (You might consider to add the mysql folder to your backup system, if you haven't.)
Your old databases should be accessible again.