If you are talking about how the task fields are displayed in the backlog view, you can change the order in this way:
1. log in as TRAC_ADMIN
2. go to 'Admin'
3. Select 'Backlogs' from the left panel
4. Choose the backlog you want to configure
5. On the page that appears, you can set the order for each field
Hope this helps
Cheers
Stefano Rago