Own and login to UpDiagram account. Select function Add project >>> Import Project.
You need to allow Trello to connect to your UpDiagram account, this only takes a few seconds.
Select the project you need to import data from Trello to UpDiagram >>> set up basic data (project name, description, cover) >>> add members to the imported project.
Confirm and agree for UpDiagram to import the project from Trello.