Why do I need an FM modulator and Bluetooth adapter in my car?
Portable Bluetooth adapters are used to transfer audio files from any device via Bluetooth to a car stereo, headphones, or speakers via a USB input.
An FM transmitter (modulator) allows you to play music from a smartphone or flash drive through a car stereo without a Bluetooth or USB input.
Modulators and adapters https://bacomba.ru/for-auto/sounds/