https://gbatemp.net/threads/mh4u-is-it-possible-to-convert-mh4g-save-data-into-mh4u.380902/
and if u understand what it means
http://pastebin.com/CXdd1GaH
"Prepping the MH4G data for 4U"
Unfortunately, we cannot simply inject our MH4G savedata to MH4U as the localisation team decided to change things up a bit. Namely it’s just one change but it breaks your guildcard if we don’t fix it: the character limit for your guildcard description text which is now 36 chars longer and therefore takes up 72 bytes more space (due to the game using UTF16-LE encoding).
By the way, the localized version does not support Japanese characters, so make sure to fix your name or whatever else important you use Japanese chars in in this step.
If you haven’t acquired plain text savedata yet, decrypt the files (pointless to go into detail since I can’t give out the tool and it’s not released yet). MH4G/U uses an additional layer of encryption for savedata and extdata which no other 3DS game I know of (except for MH4) does.
Open user1/user2/user3 in your Hex Editor of choice and jump to offset 0x12738. Insert 72 bytes of nulldata. Jump to 0x139F8 and you should see some dummy data. Remove 72 bytes of the the nullspace before the dummy data to make up for the changes. Save your file. There we go! Your user savedata is now fixed and almost ready for 4U.
The same problem applies to the card1~card3 files from your extdata. These are the only files from extdata you need to decrypt. Since you may have lots of guild cards stored there, it might be worth wrapping up a little script (pretty easy, start at 0x148, insert 0x48 bytes, move by 0x1200, insert etc.). I did it manually since I only had a few cards anyway and had to verify the guildcard size is always identical. Don’t forget to cut out the added 0x48 bytes at the end of each guildcard block.
To wrap up this step, encrypt user1~3 and card1~3.
i hope that help u..
coz i dont understand it at all.. i too convert it successfully i can go to elder hall, but my guild card is as broken as yours..