You need to mount the device to a mountpoint first, not try to just cd into it.
mount /dev/sdb1 <mountpoint>
If you do not already have a mountpoint (eg, a directory) defined, then you'll need to create one first
Note that /mnt/usb_drive is just an example, you can call it whatever you want. Once it's mounted, then you can "cd /mnt/usb_drive" and you should be able to see your data. -- J.W.