How can I find the path of an external hard drive?

I am using Virtual Box to install linux to an external usb flash drive. It gives me a list of drives:/ dev/sda, /dev/sda2 (type: ext 4), /dev/sda5 (type: swap). Which one is my external flash drive. This is very import and so I don't write per my current operating system, so please be certain. How can I find out which one is my external flash drive? Thank you!