Hello, you need to use the DUPLICATE FACE command, just select the faces you need, go to polygon menu/edit mesh/duplicate face
The fast way: select the faces press and hold shift + right mouse and choose duplicate face
* You can't use ctrl+c, ctrl+v to copy and paste vertex, edges and faces, that's why you're getting that message.
* You can't copy faces and paste them in to another object you must select 2 objects and combine them.
* You can't combine polygon objects with nurbs or subdiv objects.
Have a nice day.