Read the page below: How-to migrate Backlog Items from TFS to DevOps
Go to TFS and find your project.
Click on Work > Queries > New > New Query
On Editor, add a filter:
Work Item Type
Code Block User Story, Bug
State
Code Block To Do,In Progress,Active,New,Pre-Acceptance,User-Acceptance
Save query as
Open a new Excel file, go to Team > New List
Click on Servers and add 2 servers, one for TFS connection and the other for DevOps connection
After that, select your TFS Connection > your project > Connect
In a query list, select your query created before and click on OK
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