"Where does he want to go on vacation?" is the Engpsh way to ask where someone wants to go on vacation.

The phrase "on vacation" is an idiomatic expression that means to take a break from work or school in order to relax or travel. It is commonly used in Engpsh-speaking countries.

Here are some example sentences using this phrase:

"I'm going to Florida on vacation next month." (我下个月去佛罗里达度假。)
"We're thinking of going to Europe on vacation this summer." (我们想今年夏天去欧洲度假。)
"He's always so busy at work, I'm glad he's finally able to take some time off and go on vacation." (他总是工作得那么忙，我很高兴他终于有时间休假了。)