title_body: convert mobi to epub
upvoted_answer: Calibre (free, open source) can convert between various formats, including mobi to epub. 
  
  https://calibre-ebook.com/
  
  The command-line ebook-convert is also a part of Calibre:
  
  https://manual.calibre-ebook.com/generated/en/ebook-convert.html
  
  Also, there are third party tools to enable Calibre to remove DRM, if that is needed.
  
  https://apprenticealf.wordpress.com/