My zorin os 16 pro was not getting updatte. So I cleared all the links from sources.list.d How can I restore them?
That is not the proper solution to the problem.
Fortunately, your Zorin OS sources should still be intact in your /etc/apt/sources.list
You can plug in your Installation Media for Zorin OS (LiveUSB) and transfer over from it:
And as a Pro user, check for any Zorin related Premium files in there.