adb - How to pull mmcblk0 to a windows pc?

So here is what i want to pull : mmcblk0 whith it's size 15.7 GB.

C:\adb>adb shell
shell@android:/ $ su
su

shell@android:/ # fdisk -l /dev/block/mmcblk0
fdisk -l /dev/block/mmcblk0

Disk /dev/block/mmcblk0: 15.7 GB, 15758000128 bytes
1 heads, 16 sectors/track, 1923584 cylinders
Units = cylinders of 16 * 512 = 8192 bytes

This is what I tried:

C:\adb>adb shell su busybox cat /dev/block/mmcblk0 > C:\1.bin

I only have 1KB output with content inside said "unknown id". Also tried with pull but seems also doesn't work.

What should I do to get this 15.7 GB mmcblk0 ?