The Excel workbook Public-Folder-Migration-Actionplan-EN.xlsx spreadsheet is supposed to support you during a migration of Legacy Public Folders (Exchange Server 2010) to Modern Public Folders in Exchange Online.
The workbook consists of three spreadsheets:
If you encounter any issues while preparing for migration or during migration of public folder, I recommend to check the Exchange Server Techcommunity Forum.
Enjoy Exchange Public Folders!