File share migration to Sharepoint online

Is there a Migration that would report the folder structure on my existing Synology drive for client. It holds about 500 GB of clients data which I wanted to move to SharePoint online, so I could educate user about using links on email for documents instead of direct attachment. Online outlook does not support more than 35 MB of data transfer and I would like user to stop sending attachment and share link instead, which is only possible after I move that folder to SharePoint or sync to SharePoint.

I have fairly small amount of users and about 600 GB data migration. Out of 40 licensed users with E3 and Business premium, only five or six users would need access to clients document and only they are responsible for sharing with other Team. There $4k and 5k solution for file migration from third party solution sounds ridiculous based on the user count I have and the amount of data I need to migrate.

I would need a tool access the list of files and folder depth that are eligible to sharepoint online migration before even I copy data to sharepoint. If it shows report of files with special character, which I see a lot of regular browsing. I can educate user about renaming, if they agree or try to run script to rename, if they agree to change. Does 5000 items per document library include folder and file count or only folder count? If it is both file and folder then I may have to create sites for each individual client folder instead of room folder. However, all these are possible only after running some kind of reporting tool first