How to add real buyers to a new group in Bitrix?

Question

1C-Bitrix

Hello.
There is Bitrix: Site Management.
I need to add real buyers to a new user group.
Only those who made at least 1 purchase on my site, i.e. the buyer must have at least 1 order with the status "Completed".
I could not find regular tools in the admin panel.
Can you please tell me how to implement?
I can’t write any processing on my own (