FreeSound - The website https://freesound.org is a great source for sound effects, but make sure you read the license for any sound effect you download, you want ones that are free to use and distribute in your project.

Alternatives:

https://pixabay.com/sound-effects/

https://www.zapsplat.com/

https://mixkit.co/free-sound-effects/

and again - make sure you read the license for any sound effect you download, you want ones that are free to use and distribute in your project (most of them should be good to go).