Yes you are right, I'm sorry that I didn't read your post well enough to realise that you wanted to go cia -> Sky3DS and assumed it was the other way. It will probably work. If you have issues I don't think I can help but others will be able to.
No problem Quantumcat, and thank's very much for help and avaibility.
I'll make a feedback to conclude about the result.
Back again.
Finally the operation is extremely simple to convert backups of CIA games to .3DS games (with the SKY3DS+) !
1) Launch JK SaveManager program, whether it’s the built into the Homebrew Channel in .3DSX version, or the standalone .CIA version : the result is same thing.
2) For each selected .CIA game : export the backup.
- Choose SD / CIA.
- Select the game.
- Select Save Data Options.
- Select Export Save.
- Choose a name.
- Then validate with A button.
Repeat the operations for each of them.
3) Now leave all, and select the game that will receive the import on the SKY3DS+ (first of course you have copied a .3DS version of the same game on the SKY3DS+ micro SD card)
4) Launch again JK SaveManager.
5) Select Cartridge.
- Select Save Data Options.
- Select Browse SD for Data.
- Select the directory where you put the save before, located in /JKSV/Saves/<Name of the Game>/
- Validate with Y button.
- Select Import Save.
- Choose the name (that you had chosen to type before).
- Then validate with A button.
Repeat the operations for each of them. Don't forget to leave, and change the cartridge game with orange button.
And it's magic : you have recovered and converted all your CIA backups to your new version in 3DS format !
Tested with 4 different games, everything works!
Now I can erase the games in CIA versions installed in the internal memory of the NEW 3DS XL, and recover a lot of storage space.
I have not tested but I assume that reverse conversion is done in the same way (.3DS savegame => CIA savegame)