ReneePHi @ReneeP,
I found the Pfaff Expression Sewing Machine Owner's Manual online:
http://www.pfaff.com/SiteMedia/PFAFF/Products/Machines/expression-line/Manual/expression-3-2-4-2-manual-EN.pdf
Your manual recommends needles of system 130/705H.
These Schmetz Universal needles are also of system 130/705H which is the needle system used by most home sewing machines. These needles have a flat shank and a scarf and they should fit on your Pfaff Expression sewing machine.
For anyone else unsure if these needles fit your sewing machine at home, try checking your manual or ask me here and I'll do some research for you.
Thanks and I hope this helps!
~ Rita