こんにちはは えいごで "Hello"です / "Konnichiwa" is "Hello" in English.

こんにちは

this is a greeting expression which means "Hello.".

こんにちはは　"Hello"です。

this means "'Konnichiwa' is 'Hello'".

こんにちはは　えいごで　"Hello"です。

I put "えいごで" which means "by English (in English)".  This means "'Konnichiwa' is 'Hello' in English.".

"Hello"は　にほんごで　なんですか？

You can also ask "What is 'Hello' in Japanese?" with this sentence. If you don't know the Japanese word for the English word that you know, you can ask Japanese friend using this phrase.