If you don’t have a newer car stereo with a audio input jack, you still have options for playing an MP3 device in your car. There are wired and wireless units. The one I like and personally use is wired, the FM transmitter plugs into my cigarette lighter port. Or I guess they don’t call those cigarette lighter ports anymore, since new cars don’t come with cigarette lighters.
It is now the 12V plug and other such names.
With the FM transmitter you can set your car stereo to an unused station and set the FM transmitter unit to the same station. Then you can press play on your MP3 player and you should hear your music. If it comes in with a lot of static you can simply try setting the
units to another station. Some geographic areas are just bad, and you have to endure the static while passing through them.