You can try to loop through each column that needs to be counted and check the value of the cell. If there is a value then you can increment a counter. This approach may not be the most efficient but it should be very easy to implement.
find a quick prototype doing it dynamicly for all Columns and generates a statistic datatble with column Name and Count. Find starter Help here: Statistic_NotEmptyRowsCount_ByCol_AllCols.xaml (8.2 KB)
The Prototype was done with LINQ but for sure we can decompose it into more essential Activities if this is required