"Excuse me, how much are these altogether?"
usually you would say 几块 or 几块钱。 It's like the difference between "how much" and "how many" in English. One is for countable things and one for uncountable things. 多少钱 is like "how much money" whereas 几块 is like "how many dollars". 块 literally means "pieces" so you can think of it as "pieces of money", which is countable.
The translate ignores the "excuse me" part. 请问 is just politely indicating that a question follows, but doesn't excuse the person asking the question from interrupting someone, as the English phrase would most likely be used. And as others pointed out, "these" are not translated as well. A feature allowing Duo users who are native speakers to that language to directly suggest translations would be really helpful. Thanks.