I found Tumblr2Markdown while trying to migrate my Tumblr blog to Hugo, and decided to re-write parts of the code so that the final output needs less modification. I added a number of features as well, such as:

• Ability to output Markdown files in draft mode by default
• Download of images into individual folders (each folder name is the Markdown file’s name)
• If there are any cross-links in your posts to other posts within the same Tumblr blog, replace them with Hugo’s relref and point them to the newly exported Markdown file instead.

You can find my project Tumblr2HugoMarkdown here.