Writing ISO Images to USB

Hi everyone, I'm having an issue trying to write an ISO to USB as an image to be able to boot from USB. I a using a recent MacBook Air, and I've looked at a ton of tutorials online and still can't get it right. The main problem I'm having is that when I put the code in, which for me is sudo dd if=/Untitled/users/user1/Downloads/kali-linux-2017.1-amd64.iso of=/dev/disk2s1 bs=1m it says that there is no such file or destination, when I know I definitely have the right file and destination. Anyone know why this is happening/how to solve this? many thanks.