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. What do you mean by information? Code?
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 ?! What do you mean by 'post a new file via web page'? What is 'web page'? Your application? ZMI? (Zope Management Interface)? How do you 'post' a file?
Could you please tell me if there is a way to do that ? Could you please give me some hints ? Zope database is object database, what means it stores objects, not files, so you shouldn't expect files to be there. These are all objects. Even 'File' is instance of class 'File'. Some of these objects have methods that allow them to 'answer' to FTP requests, and you can see them in your FTP client. If some objects are not 'FTP enabled' you will not be able to use them via FTP.
Take a look at group archives. AFAIR there were similiar questions some time ago. -- Maciej Wisniowski