In order to verify if they can give you the car you requested, they need to know how long you will need the car for. 

为了更明确他们是否能给你所要求的车，他们需要知道你要这辆车多长时间。

"How long will you be needing the car?" 

 这辆车你要多久？

"How long will you be renting the car?"  

这辆车你要租多久？

"When do you need the car till?"  

这辆车你需要到什么时候？

"I'll need the car for two weeks." 

这辆车我要用两周。

"I want to rent it for one week." 

这辆车我想租一个星期。

"I need it for 4 days." 

这辆车我需要4天。

"I need it for just a day."  

这辆车我只需要一天。

They might ask you to fill out a form, or they might ask you many questions. 

他们可能会要求你填写一份表格，或者他们可能会问你很多问题。

"What is your last name?" 

你姓什么？

"What is your first name?" 

你的名字是什么？

"Are you a United States resident?" 

你是美国本地人吗？

"What country are you from?" 

你来自哪个国家？

"What is your address?" 

你的地址是什么？