Hi Larry, Welcome to the Shack.
Assuming that your Mitsubishi has a HDMI input (High Definition Media Interface) thats the plug that looks like a squished USB cable end.
That is your best bet and this way the audio is also attached to your display.
It is passable that the Sony system did not have a HDMI cable included if this is the case then you should go out and buy one or you will have to use the component outputs and inputs of the system. Component is the cable that has three "rca" ends on each end of the cable and is labeled red, green and blue.
