How do you get a jewish girls number? You look up her sleeve.
That joke seems inappropriate, what exactly do you mean by that?
I assume you are ignorant and were not aware of the holocaust reference.
It's important to be mindful of how comments and jokes about different groups of people can be hurtful and detrimental to society.  Joking about the holocaust and holocaust survivors is wrong because it contributes to desensitizing the pain that Jewish people experienced at that time.