Below is a list of asset packs/standalone SFX which will be used in game to some degree, There will be overlap of certain types of sounds and Design dept. will decide which individual sounds to use once they are testable in game
Car SFX:
https://assetstore.unity.com/packages/audio/sound-fx/transportation/vehicle-essentials-194951
https://assetstore.unity.com/packages/audio/sound-fx/engines-123836
Weapon SFX:
https://assetstore.unity.com/packages/audio/sound-fx/shooting-sound-177096
UI SFX:
https://assetstore.unity.com/packages/audio/sound-fx/free-ui-soundpack-239372
Environment SFX:
https://assetstore.unity.com/packages/audio/sound-fx/regular-impact-sounds-sound-effects-278024
https://assetstore.unity.com/packages/audio/sound-fx/nature-sound-fx-180413#content
Music:(?)
Not sure how to go about sourcing music