problem with dump system.img of exynos phone e.g G920p

i read this amazing topic and always use this toturial
but not worked on g920p 6.0.1
when i type below command :

HTML Code:

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adb shell
su
dd if=/dev/block/sda18 of=/sdcard/system.img

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system.img created on my sdcard and i copy to my pc and convert to tar file but when i flash the odin just say fail

how to dump system.img correctly on android marshmalow ?
pls help

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