Since repl.it classroom is shutting down on Jan 31, 2021, I needed a way to retrieve my assignments, submissions, and auto-grading test cases so I built a Chrome and Firefox extension to do it for all my courses in one click. Using the extension, you can get all your data as a single JSON file. I've made the extension completely free and it doesn't talk to any servers or send analytics data (as I am often touchy about browser extensions doing this...). It doesn't take more than 5-15mins to run, depending on how much data you have and it has a real-time progress bar to communicate how much data is left to get.
For Firefox: https://addons.mozilla.org/en-US/firefox/addon/replit-classr...
Tutorial: https://www.youtube.com/watch?v=MYZI_tX8Nog
If you're looking for an alternative to repl.it classroom, please check out https://codingrooms.com/ and you can also send us your export file and we'll import all your data (with full feature parity) within 24-hours. (I'm also the creator of Coding Rooms)