The only trailer hitch offered for your 2005 Volvo S40, is the Curt # C11438 that you referenced. This is a light-duty Class I types that has a maximum tongue weight (downward force on the hitch) of 200-lbs and a maximum gross trailer weight capacity of 2000-lbs. I have linked two articles that will help you with hitch installation.
I was not able to find a confirmed towing capacity for your vehicle so its a good idea to check your owner's manual (or speak to a local dealership) to confirm... view full answer...