How to export the items and categories of K2 (ver. 2.5.6) to a Joomla 2.5 to Joomla 3.0? And how to update to the latest version K2?

Hello Marcos,

You can safely upgrade but you will have to update your templates. You will at least have to update the k2_user module and the profile.php and register.php.

I think it would be better to use Admin Tools to upgrade to Joomla! 3.0 instead of migrating the content. You always grab all of K2's tables and media folder and move them but then again you will have to move your users and other core stuff as well.

PS. Always backup first!