may be he was looking 4 his book,one day he found it on a tall shelf，he can't reach it,so ,he asked himself：“how could I get that book?"（climb a stair，or use a chair to help him ） 从哪儿上去?means :where to go up (to get that book) may it be a little help^^

It makes perfect sense to me:-) When you lost your direction and ask someone how to get somewhere, you might use this sentence. And I also think it is a common expression in daily speech. for example, When you walked your way up the hill someone would tell you "You can't get there from here because the path ahead was blocked. you would ask "从哪上去？", which means what any other path can I take to get to the top of the hill. When you were on the first floor in a shopping mall, you wanted to take the elevator to the top floor. At this moment someone nearby would tell you that the elevators here were out of service today, in which case you might ask "那样的话，从哪儿上去？"

i think this sentence is incorrect, the last part 从哪儿上去? does not make any sense,or maybe this sentence exsits in a certain context

多谢 Ming Anna and Jane :)

请给出语境...否则没法回答。大家都在猜测什么意思？