Hi Bruce
The website with largest library of free sound effects is
freesound.org.
Other then that, google for sonniss sound effect library. Not sure where it’s hosted but that’s popular free package of sound effects.
The company which makes definitely the best sound effects is boom library, but their packages are not cheap. They also have a subscription model which gives you access to everything they offer, but their licence agreement is pretty serious on when and how you can use their stuff so if you’d go that route then make sure you check it out. Most movies and triple A games use their sound effects so it’s definitely top of the industry.
However, they do give you package of free sound effects of theirs if you subscribe to their mailing list, so definitely do that.
Another company with amazing sound effects is pro sound effects, but I’m personally not sure do they offer free sounds.
That’s all that’s on top of my head. Hope it helps.
Cheers