[Linux] Bootable USB stick

Hello,
my name is Teo and i am going to install Ubuntu soon, i have windows 8 now and i want to split my computer in 2 partitions.

Here's my problem, i have only 1 usb stick and i have a couple files i need in it. Can i make my usb stick bootable with ubuntu without formatting it ? I really need these files and i cant backup them in my hard drive because this is the first time I'm trying to split my computer in 2 partitions and I might do something wrong and lose everything.