At what step in the process do you get to? If the reader was no good, you wouldn't be able to pass https://nh-server.github.io/switch-guide/user_guide/emummc/partitioning_sd/
This may give you what you need:
https://web.archive.org/web/20210207164923/https://birbchirp.gitbook.io/switchguide/misc-useful-stuff/migrating-emu-new-sd
I also found the following that would be kept up to date:
https://nh-server.github.io/switch-guide/extras/transfer_sd/