If the DVD has HDMI only you would need an HDMI to AV converter.
You can't just use a cable; you need an active converter. If the TV has component video (3 RCA plus 2 RCA for audio) then get a converter that outputs that since you will get a better picture.
Depends on what connections the DVD player has and what connections your TV has, you did not give any details about either and there are hundreds of models with many different connection possibilities.
If the DVD has HDMI only you would need an HDMI to AV converter.
You can't just use a cable; you need an active converter. If the TV has component video (3 RCA plus 2 RCA for audio) then get a converter that outputs that since you will get a better picture.