Hello @philippeg 👋
From the screenshot, it seems that the module providing that functionality is https://www.drupal.org/project/content_access which has been ported to Backdrop: https://github.com/backdrop-contrib/content_access
In your Backdrop site, navigate to "Functionality" → "Install new modules", then type "content access" in the search field and click "Search". The "Content Access" module should come up in the list of results (for me, it was 3rd from the top). Click the "Add to Installation queue" link next to the module, and notice how it's added to the installation queue at the top-right of the page → click "Install" and follow the prompts.
Once the module is installed, go to the settings of each content type you'd like to configure access for, and there should be a new "Access control" tab at the top. There you will find the same interface as on your D7 site.
Try the above, and let us know how you go 😉