Need help migrating Xwiki?

Hello everyone,

Im a little bit lost. My goal is to set up the lastest xwiki version and possibily on the latest debian. I currently have on a old debian 5.0.10 hosting xwiki 2.7.1, with tomcat5.5, installed in 2011.
The first step I did was to install a new Debian VM with the latest Xwiki version, it works well. Now I wanted to transfer the existing data, the hardest part !

What I’ve tried so far :
Using this guide, I’ve attempted to import it but it got stuck :

also, the xar file’s size is very low (only 17 KB), while the wiki database is 300 Mo. What’s in this file ?

After this fail, I’ve tried to follow the Backup/Restore Guide, but I came up with a LOT of error after the databse import.

What am I missing ? What’s the best way for me to upgrade the debian and the Xwiki install ?

Merci beaucoup !
Cheers,