How to use SaveEditor codes - Dragon Quest Monsters 2 ??

https://gbatemp.net/threads/save-editing-or-ntr-plugin-for-dqm2.444419/
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This post is some years ago and this is the EXACT problem I have right now.
I have Dragon Quest 2 Iru to Luka no Fushigi na Fushigi na Kagi save data and
I want to use these SAVE EDITOR (not gameshark) codes (from here http://kaoru1127sp.seesaa.net/article/405959520.html)

The person who answered in the original question page had perfect answers for me
but unfortunately I am too late, and now he's github archive is all empty.
Also unfortunately I can't understand how to decrypt the 3DS save file to use the save editor codes.

Also I tried to get the actual Cybergadget Save Editor but the service is ended and now it's impossible to use it even I buy a Save Editor.

I would be very glad if anyone can help me or find some way to use SAVE EDITOR codes for my 3DS saves...