how to connect 4ch usb mixer with old amplifier

[pretty8000000]

I have an old konzert amplifier but i want to connect it in my 4ch usb mixer.how can i set it up to link with my mobile,tablets or laptop.pls help me.thanks

 

[americanaudiophile]

Not sure but I think that the audio output of the PC connects to the amplifier not the mixer directly.