How to set Yandex.metrics targets for clicking the "Confirm order" button (WooCommerce)?

Question

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Good day!
I'm trying to set up Yandex metrics goals for order confirmation in the basket. But elementary I can not even find in which button to "fasten" the event. The question arises, where to find the desired file? and there is a suspicion that when updating the plugin, all my improvements are deleted. Is it possible, for example, to write a function in some widget that will respond to pressing a third-party button?
Here is a piece of code for an already formed page, the button on which you need to set up an event.

Answer 1

It's easier to set a target for hitting the "order-received" page:
Or an example with javascript: