I'd put this in the audio forum for a faster response...but...
I'm guessing that you could use that cassette adapter used in cd walkman stereo kits the same way with the mp3 player......I'm assuming by your post above you have a cassette only deck....use the CD/cassette adapter and plug it into the mp3 player's headphone jack...........thats all I can think of plus your post seems kinda wierd...could be that it's 3am...hahaha
Hope I helped!!