Mount usb drive on raspberry
Plug In the USB drive
Create amount point
sudo mkdir /media/usb
sudo chown -R pi:pi /media/usb
Manually mount the device
sudo mount /dev/sda1 /media/usb -o uid=pi,gid=pi
Unmo
Make bootable micro SD for Raspberry Pi 3
Before you proceed with your micro SD card I suggest to check which cards work/dont work in raspberry https://elinux.org/RPi_SD_cards#Working_.2F_Non-working_SD_cards
Preparing the SD card
Detect the