All French phone numbers have 10 digits, starting with 0, when dialed domestically (from any French phone to any French phone). To convert it to the "international" format that will work from your Canadian phone, drop the initial 0 and start it with a +33.
A time-saving tip: for numbers you already know, like the hotels you're staying in, input the hotel's phone number in the +33 format now. This way, you can call or text it without any modifications.
Similarly, for any Canadian numbers you may be calling or texting from France, put a +1 in front of the 10 digits already in your phone. Again, this way you can call or text them without modification. Furthermore, as Nigel says, you don't ever have to change them again; this format will work wherever in the world you are, and you will not be charged extra (my initial fear) - the phone system "knows" if it's a domestic or international call and charges you accordingly.
When I put new local numbers in my phone, I use the +1 format if there's ANY chance I may want to call or text them from overseas. The only time I just put in the 10 digits is if I'm SURE I won't be calling from abroad (a local restaurant is a good example). Then, I never have to think about it again.