Your MacBook Pro should have either a miniDisplayPort or Thunderbolt port on the side.
In both cases, you need the Apple miniDisplayPort to DVI adapter. You will also need either 1) a cable that has a DVI connector on one end and an HDMI connector on the other end (preferred) or 2) a DVI-to-HDMI adapter if your cable has HDMI connectors at both ends.
There is more detailed information in About Mini DisplayPort to HDMI adapters on the Apple website.
Apple does not make a miniDisplayport-to-HDMI adapter; some aftermarket vendors do. I don't recommend them.