What type of brake pads should I run on my Shimano RS80 C24 wheels?
Standard brake pads would be ones for aluminium rims.  If your carbon rims have an aluminium/ shiny-metal brake track then this is what you want.

"Carbon Fibre specific" brake pads tend to be made of cork and cost a lot more than normal brake pads.  The braking surface has no trace of metal, and has a clearly visible carbon-fibre weave visible.  (after all you paid a lot for that rim - got to make it known!)

The group consensus seems to be that koolstop in Salmon or Black are an excellent brake pad choice.  

Your last resort options are to ask the Previous Owner, find an owner's manual for your rims/bike, or to take the bike to a LBS for a visual confirmation.