How many dishes about your dinner

dishes用得很对哦...

你晚餐有多少种菜
就这句而言嘛,可翻成
How many dishes are there in your dinner?

你给出的句子嘛,好象没有谓语(动词/动词短语)哦
没有谓语的句子是不成立的,无论是陈述句,还是疑问句.

其次嘛,about多为"关于", 是介词
在dinner前面用介词，不错，但如把about安进去,
"关于你的dinner有多少种菜", 那么就......
用in的话，是"在你的dinner中"的意思

对！当然对了！

How many dishes did you have for dinner?

我说的才对

how many dishes did u hv for supper?