Thanks Kempa for your feedback. I'll post the steps afterwards, maybe useful for other forum members
Danke!!
---------
To whom it may concern. This was my situation and maybe for some of you this could be helpful.
* It is a European New Nintendo 3DS XL, with official firmware: Version 9.0.0-20E,
* I'm running a Emunand Gateway version of: Version GW3D 10,7.0-32E
* The Gateway firmware is: Gateway 3DS Ultra v 3.7.1
Backup your current Emunand
- Remove the two screws from the downside from the new Nintendo 3DS XL
- Put the Micro SD card in a converter and stick this in your PC
- Use the #ds Multi EmuNand tool and select the drive with your SD card
- Click the option ‘Extract Nand’ and save it to a secure location
Performing the update
- Copy all the files from the archive to the root of the SD card where you extracted the emunand from
- Follow the instructions from 1 to 4 as written on the first page
- Tip: I had installed the bigbluemenu cia, that is what I used to install SysUpdater
So after the update and following this great post, I have the latest Gateway 3DS Version and the latest Emunand!
All worked out fine, thank you very much!!!!