Choosing the right product combination

There will probably be better suggestions forthcoming from other members but a few ideas from a different angle, I'd start personally looking at the two NAS devices, the data they hold and whether they could be migrated to OneDrive/SharePoint instead.  That would provide the biggest wins and the simplicity might be preferred over hooking up Azure to the NAS and how reliable anyway that would be I'm not sure. Even if you proceed with the NAS stuff, still might be worth checking out the free https://docs.microsoft.com/en-us/sharepointmigration/introducing-the-sharepoint-migration-tool and how easy it is to port data over to Office 365 these days. Also some more info here - https://resources.techcommunity.microsoft.com/cloud-migration/.