
The terminology can be confusing, but you use drives in Microsoft Graph to work with document libraries in SharePoint.
You can use /sites/{site-id}/drives
to list the document libraries in a site.
You can then use /sites/{site-id}/drives/{drive-id}/root/children
to list the files in the document library.
The response in the screen capture above includes information about SampleDocument001.pdf in the Graph Documents library.