Malformed IF statement with concatenant

Hi,

I'm pretty brand new to Alteryx (2 days) so I'm going to ask a simple question. As a business, we're moving the script from QlikView to Alteryx so it's like trying to learn a new language and I'm failing :(

Why is this formula giving me a Malformed IF statement:

If IsNull([PO Line Catalogue ID])

THEN

Null()

ELSE

[PO Line Catalogue ID] + " - " +

Uppercase([PO Line Description]) + " - " +

[PO Line Unit Price - Original] + " - " +

[PO Line UOM] + " - " +

[PO Line eClass Code]

I'm sure it's easy but I can't figure out what's wrong