At the moment there is no mechanism to migrate your layout from the WPBakery Page Builder plugin to the Visual Composer Website Builder.To migrate the site, you can temporary install both plugins on your WordPress site to redesign WPBakery pages in Visual Composer. Once all the pages are redesigned, you can remove WPBakery plugin.
How to migrate from WPBakery to Visual Composer?
How to migrate from WPBakery to Visual Composer?