nǐ / xū / yào / xiān / bǎ / U / pán / guà / zài / dào / xì / tǒng / lǐ / , / cái / néng / dú / qǔ / lǐ / miàn / de / wén / jiàn / 。

你需要先把U盘挂载到系统里，才能读取里面的文件。

You need to mount the USB drive to the system first before you can read the files on it.