Install "NTR Launcher" by Apache Thunder on your 3DS, and use this homebrew with the card inserted to start it!
You will of course also need the correct kernel for that card in the microSD: it appears to be an original R4 (except for the shape of the microSD slot...) so the recommended kernel is this one:
https://filetrip.net/nds-downloads/flashcart-files/download-wood-r4-162-f32256.html
Remember you must use a non-HC card (2 GB or less)