If you're looking for a legitimate way to update Balan Wonderworld, consider purchasing the game from the Nintendo eShop or checking for updates directly through the game's menu.

That being said, here's a general guide on how to update Balan Wonderworld on the Switch using an NSP file:

This guide is for educational purposes only. We do not condone piracy or copyright infringement.

You're looking for a guide on how to update Balan Wonderworld on the Nintendo Switch using a ROM NSP file. I must emphasize that using ROMs NSP files may not be the most recommended or legitimate way to play games, as it may infringe on copyright laws and potentially harm your console.