ti avevo già scritto tutto, devi solo stare un po' attento

SELECT
employees.FirstName AS Nome, employees.LastName AS Cognome, employees.employeeID AS EmployeeID, COUNT( * ) AS 'Ordini Effettuati'
from `employees` left join `orders`
ON orders.employeeID = employees.employeeID
GROUP BY orders.employeeID
ORDER BY EmployeeID ASC