You will need an ISBN for each version of your book that you plan on publishing (except for e-books, which can use an ISBN but do not require one). For example, if you publish a paperback and hardback version, you will need two distinct ISBNs.
Amazon can provide a free ISBN.
If you choose to use it, you will not be able to use that ISBN outside of Amazon. If you would like to use the ISBN outside of Amazon (for example, if you want to sell your book in the local bookstore, or you want to distribute your e-book on Kobo as well as Amazon), you will need to obtain your own ISBN.
In Canada, you can obtain free ISBNs from ISBN Canada: https://library-archives.canada.ca/eng/services/publishers/isbn/Pages/isbn.aspx
E-books can either use an ISBN or, if you do not plan to sell outside of Amazon, an ASIN.
The ASIN (Amazon Standard Identification Numbers) is automatically assigned to all products sold on Amazon. An e-book published through KDP does not require an ISBN if it uses an ASIN instead.