@maresrmo: Hello there,
For that
Go to => Dashboard => Catch Duplicate/Switcher => Check the option Enable Switcher for page/post and Save Changes.
Then,
Edit posts you want to switch to pages => Change Catch Post Type to Page => Update the post.
You will need to do this for all the posts you want to switch to pages.
Let me know if this works out!
Kind Regards,
Skandha