This might work...
[sql]UPDATE template
SET styleid = -1
WHERE styleid = 1 AND title LIKE 'classifieds_%'[/sql](assuming 'classifieds_' is your template prefix and 1 is your style). The next step would be to rebuild all styles so it updates the template listings per style.
I also strongly recommend you start editing your templates as FILES using your favorite HTML editor. It will save you hours of work mucking around in that god awful template editor!
https://vborg.vbsupport.ru/showthread.php?t=126738
(kind of an old version, so expect an update soon)