If you have a domain on Cloudflare, there is a beta feature that allows you to set up Email Routing. However, Cloudflare provides email forwarding, not hosting. You cannot send your emails through Cloudflare.
You can generate these codes using an online service, or using the QR generator of your choice and feeding it this text:
You need to take it with a grain of salt ;)
What’s your favorite database?
Mine is Route 53.