How do i get from welwyn garden city train station to the harlequin shopping centre in watford?

I need to go to the harlequin shopping centre in watford from wgc train station, but i am not sure how much it will cost or how long it will take. i need to be there by 9:50am. could someone help me ?
Answer
Weekday service:depart welwyn gc 07.55 arrive finsbury park 08.15cross london by tube to eustondepart euston 09.04 arrive watford junction 09.24day return ticket costs £24.20