They would continue to call your number as regular! Nothing special needs to be done on their end.

Thank you.  To be totally clear, they don’t start with 001 (or +1) and a country code?

Also when I am calling Canada from say, Spain, what prefix do I need to use to call Canada?

People calling you from Canada while you're in Europe can dial your number as they normally would, with no need for country codes or international dialing prefixes.

To call Canada while roaming in Europe, you would need to dial +1 plus the 10-digit number you're trying to call. (1 being the country code for Canada and the + being the international dialing prefix) dialing the numbers for the international dialing prefix (00 or 011, etc.) will also work, but if you dial the + the phone will automatically use the right prefix for whatever country you're in,

To call European numbers while roaming in Europe, you should generally be able to dial the number without any country codes or prefixes, although your mileage may vary.

Thank you very much; that is very clear.