Have you tried using DATEDIFF?
DECLARE @start DATETIME, @end DATETIME
SET @start = '12/28/2023'
SET @end = '12/27/2024'
SELECT DATEDIFF(week, @start, @end)
A caveat here is that weeks worked isn't well defined. This is the # of weeks between 2 dates but might not line up with what you consider to be work weeks. For example it doesn't take into account holidays or weekends. If you need that then the calculation will get a lot more complicated as weekends need to be removed and holidays are not a fixed list.