I have a Sony lbt d359 hifi system, I wanted to connect my DVD player so that I can play mp3 disks on it but the phono input

You are looking for these connectors on BOTH Sony and DVD:

Optical/Toslink.

or

AUDIO OUT to AUX IN/AUDIO IN/LINE IN.

If these connectors exist, again on BOTH boxes, then all you need is the proper cable.