once you scan the QR code what is meant to happen is the Switch
switches your wifi over to a wifi hotspot the Switch created. If you don't connect automatically then go into your wifi settings and see if there is a wifi called something like "switch_4155A1123" and try connect to it. once you are connected to it then you should get a second QR code to scan and you'll be taken to a webpage where you can download your pictures.
it's a bloody mess the way Nintendo have implemented it.
here are some pages showing how to do it:
The most direct way to transfer screenshots and videos
www.nintendolife.com
Did you know you can share screenshots and videos with your phone from your Nintendo Switch? We'll show you how!
www.howtogeek.com