How can I sell my extension on marketplace?

I have developed extensions for PrPro and Au.
This works fine as long as it is in my local folder.
How can I sell it in the "marketplace"?

Here is what I have researched and tried.
- I went to https://developer.magento.com/extensions/.
- Zipped the extensions folder according to https://devdocs.magento.com/guides/v2.3/extension-dev-guide/package/package_module.html and sent it to them.

- What I don't know -.
Can I sell my extension on marketplace if I follow the magento page above?
Or is there a completely different way?
I don't know how to write module.xml or composer.json if I follow the above page.