do you have to buy unity plus or pro to build to 3Ds or nintendo switch?

do you have to buy plus or pro to build to these consoles?

 

No, but you will need to create a Nintendo Developer ID account:
https://developer.nintendo.com/

The process is explained here: https://developer.nintendo.com/the-process
FAQs are listed here: https://developer.nintendo.com/faq

Be sure to read everything carefully. For instance: If you're not of legal age (yet), then you're out of luck.