Zend certified PHP/Magento developer

Merging Live and Dev Databases from 2.19 to 2.3

Since, the magento 2.3 requires PHP 7.2 my current live is has PHP 7.0. I copied the live site to staging server upgraded my magento to 2.3.

And everything seems to be working, I plan to change the DNS setting once I go live with the staging. what is the best way to get the new orders and customers information from live site to the developing site before i go live?