To create new Facebook listings, the ISO Country Code is required as a separate value for a complete international phone numbers. You can include the Country Code number (just the number, no plus sign or other marking) in column Q of the 'Create New Facebook Listing' Google sheet in Bulk Management -> Create Facebook listings. You will see from the image below all of the required field marked in red.

Country codes are numerical prefixes used when dialing international phone numbers. They are used to indicate the country where the call is being directed. Each country has its own unique code.

Unsure of what your Country Code is? You can search for your specific Country Code Here.