SELECT Count(*) AS EmpCount FROM employee where group =
Comboboxes are confusing, the .Text property may not be what is actually selected, so use the SelectedItem. SelectedItem is an object so you have to convert it to a string.
Also note that the "=" operation in SQL is case sensitive, so if the case does not match exactly, then the count will not be right. To do a case insensitive search, use "LIKE".
BTW, (as my comment says) you should learn about SQL injection attacks, and how to use parameters in SQL statements to avoid them.