threeSD VS 3ds-save-tool

Recommend using threeSD. Not only will it get the AES key, but also has the option for dumping installed titles, DLC, save data, etc. Obviously, if the only thing you want is the AES keys then you can deselect everything except that and there will be no problems.

You have to hack your 3DS to dump data from it. This is very safe as long as you are careful. You can use threeSD to dump data (recommended by Citra developers).

- threeSD tool: https://github.com/zhaowenlan1779/threeSD/releases/tag/v0.5.4

This is a helpful guide for doing it manually but you can also use threeSD to do it automatically

First off dump your system files using ThreeSD and make sure that you already have the update installed for Mii Plaza on your 3DS so that ThreeSD dumps it. Also make sure you have ticked System Settings and Config Savegame when dumping with ThreeSD. If you don’t know how to dump your system files from your 3DS use this guide.

If you want, you can run Godmode9 via ntrboot on your non-CFW 3DS without having to install CFW – though this is a somewhat atypical process. You might even be able to use threeSD, but it may require some modification as Godmode9 via ntrboot cannot dump boot9.bin. Or you might be able to use ninfs on your PC.

I'm not sure but you can try to use threeSD to extract the save from you SD card

You're welcome. You can try this program to get your files off of your SD card. https://github.com/zhaowenlan1779/threeSD

I believe the streetpass feature is stubbed so it doesn't really work in the way of Streepass 2 Rise from the Ashes. I've been able to extract the streetpass files from the googlesheet by using this. Unfortunately when I put the files in the Citra user directory, it's not detected. I've gotten around this by doing this on my 3DS and transferring the Streetpass Plaza save file to Citra.