Export userdatabase into mysql

Hi!

Is there any chance to export the userdatabase (that already exist) to soma kinda text file or so?
I merged 2 galleries into phpbb, now the whole thing uses phpbb's userdatabase, but i would like to fill it up with old users' datas.
(so new users could use gallery with phpbb registration, and i would create a new user for all old users, from this exportfile)