[Zope] Extracting all files from Zope DB

Hello, In order to migrate from Zope to "..." (I don't know yet), we are trying to extract all the information located inside the Zope database. I've found the FTP interface to the Zope database, I can browse inside the subfolder but, I can see any files !? If I post a new file via the web page, a folder is created (I see it via FTP) but the folder is empty ?! Could you please tell me if there is a way to do that ? Could you please give me some hints ? Thank you very much ! Jerome Nokin