Because this is a "part2" file, it cannot be opened on its own; it must be combined with "part1" (and any subsequent parts) to access the contents.
Right-click ONLY on part1 and select "Extract Here" or "Extract Files..." using a tool like WinRAR or 7-Zip .
.NSP is a standard format for Nintendo Switch digital games.
The full game is approximately 14.6 GB , so ensure you have enough space on your SD card or PC before extracting.