Nintendo Switch save files are stored directly on the console’s internal memory, and there’s no way to move them to an SD card or anywhere else.This means that you cannot backup your saves, or transfer them to another console.
Furthermore, there is no cloud save feature, and Nintendo isn’t planning on adding one any time soon. Right now, the only control Nintendo Switch users have over their save files is deleting them when they need to clear some space on the 32GB internal memory.
This is a rather odd decision by Nintendo, as users can re-download their game on other Switch consoles. Game purchases are tied to the Nintendo ID, and not the console, so once you log in to a second console, all your games are available to you; but not the save files.
If you’re playing The Legend of Zelda: Breath of the Wild right now, you better pray nothing happens to your save file or the console you’re playing it on. There isn’t any way for you to recover your progress as the moment, so you’ll have to start the whole thing over again.