I am trying to figure out the same thing. I'm trying to figure out how to transfer over vendors' information and transactions that my new assistant had entered into her computer, over to my main computer that has the QB Desktop Contractors Edition 2019 originally installed on. 

I backed up what I had originally on an external, then downloaded it onto her computer here at the office so that she could enter vendors and their information, but now I'm wondering how to merge the two to update my main QB account with the information she has entered, without losing what I have recently entered on my own. 

 Any advice?  Thanks!