Hello,

In general you can use the built-in export functionality to export data from Kentico: Export.

Or you can try to get the cotent of your documents etc. programatically with the use of database tables: Documents API database tables.

But let me kindly inform you that the structure of documents and database is more complex than in the WordPress so this scenario is not supported from our site and I believe that never will be.

Best Regards,
Martin Danko

Why do you want to move to Wordpress? Always wondering what features it has over others.

To simply get the blog posts you can get the data from the database pretty easy although it won't have everything you want. Just run

SELECT * FROM CONTENT_BlogPost

And it should get you the posts with the basic info. If you want more, you'll have to follow what Martin suggests.