moves files or directories from one place to another

adb shell mv /mnt/sdcard/Download/test.txt /mnt/sdcard/DCIM/test.txt

Force copy by deleting destination file

adb shell mv -f /mnt/sdcard/Download/test.txt /mnt/sdcard/DCIM/test.txt

Interactive, prompt before overwriting existing DEST

adb shell mv -i /mnt/sdcard/Download/test.txt /mnt/sdcard/DCIM/test.txt

No clobber (don't overwrite DEST)

adb shell mv -n /mnt/sdcard/Download/test.txt /mnt/sdcard/DCIM/test.txt