How to track the triggered button?

Question

JavaScript

You need to set up an event for analytics in the google tag manager on a button click. But only when it redirects to the payment site. Those. when the form is filled out and the person after clicking goes to the payment site.
Question: how to correctly catch the id of this button at the moment of redirection? or how to make a target in GA or gtm in another way?
Page with button