If your new TV only has one non HDMI input then you have two options. You can buy an external switch box to expand that one input. If your connections have three RCA cables (usually red, green, blue) for video and two for audio then you need one that does component video. If you have a yellow RCA for video and 2 for audio then you need one for composite video.
The other option is to buy a cheap bluray with HDMI and use that instead of the DVD player. Your receiver will use the one input you do have.