Retain document "most viewed" when migrating to a different SPO site?

Hello!

We are currently in the process of moving our outdated site/subsite hierarchy to a flat architecture, but are running into some issues with "most viewed" documents. 

Is there a best practice to copy/move documents from one library to another and retain the most viewed information OOB? I've tested the copy component, but before testing a Move option, I wanted know if I was heading down the right route.

If it is not possible OOB, are there any third party tools that I should look into?

Thank you!