Okay, yes, this is older technology & cars don't have infinite, universal backwards compatibility. Cars have Bluetooth & they think that just fixes everything....well...not quite.
Maybe there are other fixes & other workarounds, but you need to employ old(er) technology solutions to fix this old(er) technology problem. You need a (QUALITY) FM transmitter that will plug into your aux, blast the signal as an FM radio station, and you tune your radio to that station & listen. Notice I said QUALITY...most of them are kinda crap & you have to deal with static. I have no specific brand, model suggestions. Good luck.
A better but more expensive solution: upgrade your car's head unit. Stock head units are shit, anyway. 🙂 Get yourself a nice head unit with 3.5mm aux connection & aux in that iPod, if your budget allows. THEN, you'll have the best sound quality and also Bluetooth connection, etc.
I wish you well, music makes the driving experience, I hope you get EVERYTHING you need. 🙏