Update spmt.md

Author: wenhua-helen

spmt/spmt-ps/spmt/spmt.md

@@ -8,6 +8,8 @@ Locale: en-US
 # Microsoft SharePoint Migration Tool
 ## Description
 The following migration cmdlets are based on the SharePoint Migration Tool (SPMT) migration engine. It will move files from File Share, SharePoint 2013 document libraries, or items of SharePoint 2013 lists to Office 365.
+Notes:
+In order to support migrating file path up to 400 characters, PowerShell 5.0 and .NET 4.6.2 are required. 
 
 ## Microsoft Teams Cmdlets