What name in yiddish would be translated to Arthur in English?

None. There is no Yiddish name that has the same meaning as Arthur, mainly because the meaning of Arthur is unknown.

Arthur could be derived from the Celtic elements artos "bear" combined with viros "man" or rigos "king". Alternatively it could be related to an obscure Roman family name Artorius. Arthur is the name of the central character in Arthurian legend, a 6th-century king of the Britons who resisted Saxon invaders. He may or may not have been a real person.