Hi,
in the documentation there is an article on what you have to do in order to be able to migrate Visforms with a Joomla! update from 2.5 to 3:
www.vi-solutions.de/en/documentations/vi...omla-2-5-to-joomla-3
In the instructiions it says clearly, that you have to check for the proper Visforms minimum Version on your Joomla! 2.5 installation first before you run the Joomla! Update and update at least to Visforms 2.0.0.
"Choose submenu "Manage" and find the entry of component Visforms in the extensions list. Determine the version of Visforms you use. If it's lower than 2.0.0 go to the download menu on our website and download the newest Visforms 2.x version. Install this version (without uninstallaling the previous one!) via Extensions Manager."
Sadly if you have not installed at least Visforms 2.0.0 on the Joomla! 2.5 installation, it is not possible to update Visforms after Joomla! has been created to 3.x. I'm not even sure if you can uninstall Visforms in this case through extension manager. You could try, but if unistalling works this will remove all forms, data....
You have to go back to a backup of your Joomla! 2.5 website and run the required Visforms update first, than, do the Joomla! update again.
I'm sorry for your problems,
Aicha