Not so fast. The adaptor kit
http://robotstore.gr/el/xbee-adapter-kit.html
is on a website with no english. You can't buy it there unless you can find out if it includes the xbee shown plugged into it because if it does you DON'T need the xbee modules in the other link , right ? Look for the same product on an english website and/or send an email to the first website asking if the kit is AS SHOWN WITH the xbee.