Probably the wrong question. Do you know what country the umbrellas were made in?
If you do you can check the Canadian Border Services Agency website for the product and the country of manufacture.
Canada has so many free trade agreements nowadays that you may not be charged any duty at all.
What you CAN count on is a service/brokerage fee by the shipping company. This can vary from $9.95 to Canada Post to a minimum of $25 (ascending with the value of the item) from a courier like UPS.
In addition, the umbrellas would attract PST/GST/HST at the going rate in your province.
Few sellers would ship something as bulky as a patio umbrella by post, but it is usually the least expensive method, with the border clearance charges. And sometimes the postie doesn't bother collecting those fees at all. Couriers ALWAYS collect their fees.