Making cookies and need to know , my cookie recipe calls for a cup of butter and I have unsalted butter do I need to add salt to this recipe to make up for the salt that's not in my butter? Also how much thank you

No. Unsalted butter is better. I have used it just recently and made wonderful cookies (one of which I just finished eating and am still wiping crumbs off my lips).

I agree, unsalted butter tastes better. I leave salt out of just about every recipe anyway, except yeast bread.