Hi @milan88,
I was able to find this: GitHub - ualbertalib/ojsxml: converts a csv file to ojs native import xml - from the University of Alberta Libraries. I can’t vouch for it specifically, as I haven’t used it, and I don’t think it’s been tested for use with 3.3, since 3.3 is so new, but it might be worth trying. Still though, I would recommend trying to work through the upgrade rather than exporting and importing content, because if you do that, you will lose all of the associated data (e.g. reviewer, editorial history, etc.)
Best regards,
Roger
PKP Team