Hi,
As neither the Beocenter 8500 or the Beogram 3300 have a phono stage built in, you will need a separate phono stage in order to connect them. One example is the one linked below from my website, which comes with all cables needed and full instructions, ready to “plug and play”:-
https://soundsheavenly.com/beogram-record-players/12-2196-pre-amp-bundle-for-bo-beogram-and-all-turntables.html#/36-output-5_pin_din_aux/41-power_supply-uk – please choose the “5 pin DIN plug” output option for your Beocenter.
For reference, Beogram 3300 is an earlier model from just before B&O moved the pre-amplifier from the music system to the turntable, whereas your Beocenter 8500 is the later model from after this change. The change meant that it was possible to have more freedom over the placement of a later turntable - the inclusion of the pre-amp in the later Beogram 3500, 4500, 6500 and 7000 meant that they no longer needed to be kept close to the music system as they gave a higher signal output.
Kind regards, Steve.