move email accounts from GoDaddy to onsite Exchange

Hello, I actually have two questions

1.  Our domain is hosted with GoDaddy, I want to point https://mail.XXX.org to my onsite exchange server.

2. I need to move my user's external emails Usera@XXX.org to their local exchange email Usera@XXX.local

Thanks for any help you can give in this 

I'm new to this