Hi Memo,
S45 are good speakers, although they are quite old now so the condition may not be as good as when they were new.
As your speakers are passive (ie. unpowered), they will need to have either a Beolink Passive, MCL2P or an audio amplifier of around 30 watts or more connected between the B&O audio system and the speakers to boost the signal.
If you are using Beolink Passive or MCL2P, you need this cable to connect it to the B&O system:- link
If you are using an audio amplifier (non-B&O), you need this cable instead to connect it to the B&O system:- link
You then just need standard speaker cables to connect from the Beolink Passive, MCL2P or amplifier to the speakers:-