I have two website abc.com and xyz.com (cloned). I would like to redirect customer from my cloned (xyz.com) website to the main site (abc.com) when they click to “add to a cart” button.

Please advice
Thanks

Here is how I would do that.
Do not show the standard add to cart button.
Use a custom field to create my own add to cart button.
Use excel to create the links for the buttons. (thousands or products can be done in just a few moments). (hint - ASAP utilities for excel (merge columns)).
Upload your custom buttons via CSV utility.

I would have a message there to be very clear that the user is being redirected to your other website.

Thanks for your prompt response. How do I create custom checkout button?

Thanks

the code would look something like this