You will need phpMyAdmin for this, this will by kind a surgery. This is joomla 2.5 to 2.5.
I am migrating from site A to site B, same template and everything but i had a problem, i imported a Database that was out of date and now i need only import some k2 items and i want to avoid to redo everything again, so by analysis the K2 tables in my DB i found the next tables are involved: (the ces_ is my table prefix it may vary from yours).
In my case the categories and users are the same so i don't care about them, but you can extract them from k2_categories and k2_users accordingly.
In PhpMyAdmin go to search tab and set your criteria, in my case 42 is the super user that created the items i want to move (i found this at the k2_users table):
SELECT * FROM `ces_k2_items` WHERE `created_by` = 42
How to export query results on PhpMyAdmin:
make sure you copy the images stored at:
The just simply import the rows you already exported using your SQL criteria to your DB using the import tools of phpmyadmin.
This procedure worked for me i hope it helps you.