Q: Does iPad 3 support CANON MG1820

Hello there, nancylkaye.

It sounds like you are trying to use the AirPrint feature of iOS device. The following Knowledge Base article is a great reference for AirPrint and the most up-to-date list of Airprint-enabled printers:

Print from your iPhone, iPad, or iPod touch - Apple Support

You can print from your iOS device to any Airprint-enabled printer:

1. Open the app you want to print from. Find the print option by tapping the app’s share icon ( or ) or settings icon ( or). If you can’t find the print option, check the app’s User Guide or Help section. Not all apps support AirPrint.
2. Tap (  ) or Print.
3. Choose an AirPrint-enabled printer. 
4. Choose the number of copies.
5. Tap Print.
   
   

If you don’t see your printer, make sure that:

• Your iOS device and your printer are both connected to the same Wi-Fi network and you're within range. 
• Your printer supports AirPrint.

Thanks for being part of Apple Support Communities.

Cheers.