For most Apple iPhone models, you can go into your device, Settings > General > About and scroll down until you see the string next to IMEI.
If your own phone is blacklisted, and you’ve recovered it and want it usable again you can call your carrier (Rogers, Bell, Telus, etc) to get it removed. If you’re looking to buy a second-hand or preowned iPhone and the device IS listed on the national blacklist, it WILL NOT be usable as a cell phone in Canada or the United States.
You CANNOT use blacklisted phones on any cellular carrier in Canada or the United States. The phone can basically be used on WiFi and as a iPod.