I want to buy two kilos of pears.对two kilos of 进行提问该怎么问?能不能用how much pears do you want?进行提问，

如果对方知道你想要梨，就直接说：How many do you want?
否则就说 How many kilos do you want?

不能用how mang pears 一定要加上kilos

不能用how much ,how much 是用来表明不可不数名词，简单来说就是后面不能加s变复数的，例如How much money 而不能用how many money

How many pears do you want to buy?

How many Kilos of pears do you want to buy?
问题补充：能不能用how much pears do you want?进行提问,
不可以,much 提问只能用于不可数对象,pears可数,必须用many.kilo也好,pears也好,都是可数名词,所以无论你提问哪个都需用用many：
How many pears do you want (to buy)?
How many kilos of pears do you want (to buy)?
就two kilos 提问,应该是第二个答案.第一个问的是买几个.

考特殊疑问句吧？ 如果是这样就是：
how many kilos of pears do you want to buy?
如果只是简单的口语，则可以简化：
how many do you want?
how many kilos do you want?
how many kilos of pears fo you want?