Unfortunately I think I will have to dissapoint you. CR80 Radio Cassette does not have AUX input. That feature has only MP3 player model.
Yellow connector on the back of the head unit is for amplifier since that is part of ISO C connector which is not used on your car.
https://www.tehnomagazin.com/Auto-ra...-Connector.htm
https://en.m.wikipedia.org/wiki/Conn..._for_car_audio
https://www.the75andztclub.co.uk/index.php?thepage=ice