Here's a start,
TOTAL( SUM( IF DATENAME( 'weekday' ,([Order Date] ))='Saturday'
OR DATENAME('weekday',([Order Date]) )='Sunday'
THEN 0 ELSE 1 END ) )
But it does NOT take holidays into account. And you'll have to set up the first 7 days part, since I don't know how you're viz is set up. (In the future, if you include the whole Tableau window in the screenshot, so we can see the pill arrangement/colors, we have a better chance at guessing what's going on.
As to Holidays, I'm fairly certain it could be done using some sort of look up table, but it is definitely NOT of the software, though often asked for.