Generally speaking, dogs and chocolate do not go well together.
Here’s a national geographic page that charts how much chocolate it takes to kill your dog. If for some reason that page link doesn’t work (as I’m finding sometimes it works and sometimes it doesn’t), just go to national geographic.com and search for chocolate.
Do note….some dogs can eat a chocolate bar and be just fine, whereas another dog the same size and weight can do the same thing and NOT be fine. Just like people, different dogs have different tolerances for things that perhaps might not be the best in the world for them to have.
In fact a better link would be right here.