Here are steps about how to migrate file shares to SharePoint Online using Microsoft SharePoint Migration Tool.
1.Open SPMT > sign in > Start a new migration
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2.Copy content from File share.
3.Select the source of your files(local computer or network file share) and you could select migrate selected “folder and folder contents” or “migrate only folder contents”.
4.Copy content to SharePoint.
5.Type SharePoint online site URL where you want to migrate your content > Select document set you want to migrate to
6.Now you could name your migration and you could add another migration.
7.Choose migration settings in “view all settings” > Save > Migrate
