oui,

Zim stores your documents as plain text files in its particular wiki syntax, e.g., what you see in the text area the word hello in bold is converted to its wiki syntax as **hello** when your editting document is saved (Note that the saving is done automatically by Zim). Your documents should be located in a folder called Notes or something like that, check to see if you can find one in your home directory, or under the Documents directory.

I suggest you read something more about Zim on its manual page

http://zim-wiki.org/manual/Start.html