Just 1 for each country, in the application form you may need to list all of the addresses you have been living in the country.
In general, you and all the people in your family who are 18 or older need to collect police certificate from all countries or territories that you or family member have spent six months or more since the age of 18.
For example: if you visited, worked or lived in a country for two months, left for a few years, then returned for four months, that counts as spending six months there. In this case, you would need a certificate.
If you need a police certificate from a country or territory and:
- are currently living there, or received the police certificate before leaving, the police certificate must be issued within six months before you apply.
- have lived there in the past, the police certificate must be issued after you last lived in that country or territory.
Link:
https://www.canada.ca/en/immigration-refugees-citizenship/services/application/medical-police/police-certificates/about.html