Connect classic SharePoint team sites to new Office 365 groups
To assess whether your SharePoint site collections are ready to connect to Office 365 groups, use the SharePoint modernization scanner tool. This tool can help you plan out your site modernization strategy and will create an in-depth report, including areas that need attention.
If you want to allow site collection administrators to connect classic team sites to new groups from a new menu command we're adding, you don’t need to do anything. If, however, you want to disable this option, you will need to change the default setting. Learn how. Note that global and SharePoint admins in Office 365 will always be able to connect sites to new groups using the PowerShell cmdlet or API.