Translation:How do you say this character in Chinese?
"how is this character pronounced in Chinese": What does this even mean? In Mandarin as opposed to Cantonese? Or Japanese? If you imagine a Chinese learner from e.g. English background, he would ask: "How is this character pronounced?", not "How is this character pronounced in Chinese?"
That would be: …中文怎么说？ where you replace the … with the word you are asking about. If you want a direct translation of "How do you say this English word in Chinese?" (perhaps you are a Chinese speaker pointing to a long English word in a book, and you want your friend to translate it into Chinese for you,) you would say "这个（英文）词中文怎么说？” Note: "English" could be 英文 or 英语.
Does 字中文 belong together? I first thought that it stands for "Chinese character" and should be written 中文字.
But now I see, maybe 中文说 means "...say in Chinese..."
How do you say this character in Chinese?
How do you say this character in Japanese?
Can anyone confirm?
It's not 中文字 because you're asking about the Chinese reading of a character, as opposed to the Japanese or Korean reading. For example if you know 水 is read "mizu" or "sui" in Japanese but you want to know that it's pronounced "shui" in Chinese.
Imagine asking in French, how to pronounce this word ("grand" for example) in French.
The correct answer should only be: "How do you say this chinese character" (when 字中文 translated to be Chinese Character). While :"How do you say this character in Chinese? Means how to say in chinese for any character be it English/latin character or Hindi character or Thai character etc. Any other opinion?