calculation of the dates set by the criterion

[provaid82]

Hi guys
I have some difficulty, or rather how to do minor formula for calculating the dates given criteria
So here is the condition
I have two columns in the first I've introduced a product which is divided into three types-Cap, T-shirt, Shirt
In the second column I've entered the dates on which I've sold
Now I want to calculate the date on which the fifth Hat is sold for a period of 31 days from today
I also want to calculate the date on which the hats sold will be less than five issues from today
You will get the file if someone is easier to do instead of explaining it
I saw the formula will do for the other criteria