I think you need to look at the “w” pattern when using parseDateTime. This is the week in the year. You’ll also need the year for this to make sense. So for the start date where $WeekOfyear and $Year are string with the week in the year and the year respectively, I think you need
parseDateTime($WeekOfYear + ' ' + $Year, 'w YYYY')
and the end of the week will be 6 days from this value, so if you saved it in $StartDateTime, you’ll need
I’ve put an example microflow up to show you how this can work.