Here is a link to the service manual for your amp. Go to p.14 where in the parts list it specifies that the Volume potentiometer VR301 , part # 211-0902-009 is a 30k Ohm potentiometer.(see right hand side just above Capacitors Group Heading).
Unfortunately, searching online for this part using the Denon part number produces no results.
Also the manual doesn't specify the Volume potentiometer's power rating. You may be able to work this out by removing it from the unit and then simply 'sizing' it against replacement ones which have the same type of connections, (or close enough as you most probably will have to un-solder the old and solder in the new) the correct length shaft and the body size to suit. (Look online at Jaycar, Altronics, Element 14).
Alternatively just get the highest power rated one that will physically fit in, as long as it is 30k Ohms. 5W or 10W should be more than adequate if they fit. It will possibly be only a 1W as it is most probably only adjusting the gain of the audio power transistors and is not in the direct output feed path.
Hopefully this is of some help.