Welcome to Beoworld! Please can you clarify what the “Beosound 8000” is, as I haven’t heard of this? Do you mean the Beosound 9000 6xCD player or the Beolab 8000 pencil speakers please?
I can then help you to connect this to the Beomaster 3500 (flat tuner/amplifier with grey top panel) once this is known.