Try out the method that seems easiest and if it doesn’t give what you want then try the next and the next and then post back on what you found.
Have you read the Jekyll docs?
For Blog Migrations it points to Jekyll Jekyll importer which handles Wordpress (self hosted) and Wordpress.com
If you have issues separating your theme and content, I’d say then see you can use WordPress itself to export your content as CSV or whatever. Even an RSS feed of pages and posts. Then you can use that to build the pages of your site.
Then you’ll have to find someone who made a Jekyll theme of the exact Wordpress theme you made. Or you’ll have to find a close theme or build your own theme