File > Export > MD - Markdown will export the structure with notebooks as folders containing the notes as markdown files. The titles of the markdown files will be the titles of the notes.
File > Export > HTML - HTML Directory will export the structure with notebooks as folders containing the notes as HTML files. The titles of the HTML files will be the titles of the notes.
Any resources (attachments) will be in a separate folder. These use the Joplin naming convention (i.e. a long unique string) so that links will work.
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