ROM sites are a haven for viruses. When you search for "Super Mario 3D World NSP download," you are entering the wild west of the internet. Many files are disguised as ROMs but are actually (locking your files) or cryptojackers (using your GPU to mine cryptocurrency without your knowledge).
The game officially known as was released for the Nintendo Switch Go to product viewer dialog for this item. Super Mario 3d World Rom Nintendo Switch Download
However, for those still interested in downloading a Super Mario 3D World ROM on the Nintendo Switch, several factors must be considered: ROM sites are a haven for viruses