Hello,Where are you from?=你从哪里（or哪儿)来？=nǐ cóng nǎ lǐ lái =nǐ cóng nǎ er lái ? and this question is mostly used to ask the listener's nation. so you can say"我来自中国“=wǒ lái zì zhōng guó=I come from China. And if you ask "你们的家在哪” it should be translated as "Where do you live?" And if you don't mind,I would like to polish your sentences above. 一个时间 is incorrect, time=时间，uncountable,so you can't use 一个，一个=a/an you can say 一段时间=an amount of time=period The last sentence you wrote is incorrect,哪一个生词我用 the right order is 我该用哪一个生词？= which word should I use? In Chinese ,we mostly put subject at the beginning of a sentence. Just my humble opinion,hope it works~

In fact, North Chinese like speaking "哪儿"， and South Chinese use "哪里" more。Their meaning is same, means "where". If you are sure your pronunciation is good, maybe that guy who can't understand is South Chinese

At first, the question "你们的家在哪儿" is okej for me, but it is like where is your home address, if you only ask one people, you remove 们, if you want to ask where are you come from, you can do it like this: "你的老家是哪里的" ni de lao jia shi na li de ：）

你们的家在哪儿？ means u r asking their address. where are you from = 你从哪儿来 = 你从哪里来