If you're waiting for updates to ninfs on this resource page, you should check out the alpha releases on GitHub. This resource will be updated once a new stable release is out.
Each part is expected to end in two digits (e.g. rawnand.bin.00, rawnand.bin.01, ...). Any part can be selected, the program will search for all parts starting with 00.
The command line argument -S or --split-files is used for a split backup.
The GUI will attempt to automatically detect this based on the filename.
GUI: Automatically detect Nintendo DSi NAND backups
GUI: Fix oversight breaking automatic detection of Nintendo 3DS NAND backups
ExeFS: Always show code-decompressed.bin, even if .code is not compressed
Man bought a $20 a gauge at Amazon that was all fancy digital went to hook it up did t detect shit, then went back and bought an analog worked right away