This article explains how to find your Office 365 tenant name which is required when creating a connector for Office 365 migrations and coexistence.
OneDrive for Business Service
Login to Office 365.
In the App Launcher, click on the OneDrive App to open in your browser.
The url will look like https://tenantname-my.sharepoint.com/personal/<your user name>/_layouts/15/onedrive.aspx
Your tenant name in the left part of -my
In the App Launcher, click on the SharePoint app.
This opens a URL like https://tenantname.sharepoint.com/_layouts/15/sharepoint.aspx
Tenant name in the left part .sharepoint.com