Two different Asterisks-transfer call

Hello everyone and thanks to anyone that answers. I have a question about setting up some call transfering. Say i have an asterisk in one city and i have the “sales” queue with 2 extensions. If i get a call from outside from someone who wants to talk to a sales representative but those 2 extensions are unavailable or busy i want that call that was meant for the “sales” to be transfered to another asterisk in another city and another extension from another “sales” queue to pick it up. The call that i want transfered is a normal call from outside asterisk so it’s not an “in buisness” internet call. I am guessing i would need to know both asterisk’s IP’s for that and a few command lines in sip.conf and extensions.conf but i’m a beginner at asterisk and don’t have the knowledge to do this. Any help is greatly appreciated.
Thanks a lot and sorry if it’s a stupid question.

Treat the other Asterisk as though they were a service provide except don’t register and use static addresses at both ends.