Edit your tasks
You can edit a task by double-clicking on it in your task list, and editing the properties in the corresponding Outlook task. For example, you can change the name of a task, the due date, the priority or the status, and you can add notes and attachments to the task. The changes will be reflected in your task list.
The task number is not a property of the Outlook task. To change the task number, right-click on the task, and select Edit task number:
This will give you a dialog box that allows you to change the number.