I'm very new on Magento 2 framework. Can anyone help me from this problem? I Don't know how it actually product returns work. Is there any standard Magento logic for returns or can you advise on plugin?
It depends on magento edition. In magento 2 enterprise or community edition it is by default but in community version it is not there by default. Either you have to built custom solution or buy a plugin. I recently used in a project which is free extension.
You can use this extension : https://landofcoder.com/magento-2-rma-extension.html It is free and working correctly on magento 2.3 community version.
Magento 2 extension installation guide : https://magefan.com/blog/how-to-install-magento-2-extension-2/
Please let me know if any other information you required.