Thanks for posting your question in the Microsoft Q&A forum.
To modify the order numbers of test cases in Azure Test Plans, particularly when you have uploaded a CSV and need to adjust the starting order number:
Since you’re unable to see the "Order" column in grid view, it might be that you're working in a view where the "Order" column is not displayed by default.
If you need to adjust the order numbers and the manual reordering in Azure DevOps isn't sufficient or feasible, you can modify the order in your CSV file and re-upload it.
Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful