i have a dell optiplex3050 desktop computer   i am trying to heek up a camera and mic up to it but i only have 1 port in the front     i have tried the front and back port but mic is not working  my plugs are a  trs and it says the computer hookup will use either   is there a adapter i can get for my 3.5mm to put it  thru my a usb port   thank you