The biggest problem with leg bands is that there are no standards. What is stamped on them is entirely up to the breeder, and there's no database where the numbers are kept, except for the breeders personal records if they choose to keep them. There are some common formats. Typically, the first letters correspond to the breeder. Might be a person's or company's initials. Middle part is often the state in the US, or Quebec in your case. The remaining part is generally a way for the breeders to identify them. Some refer to date and clutch number, or clutch and baby number, that sort of thing
Again, no standard, so it's whatever the breeder chooses to use. If you can find them, they may have the info you're looking for.
I might start by search for breeders in Quebec with initials YP. Needle in a haystack for sure, as many are back yard breeders and not registered or listed anywhere. Some are horrible mills that breed and sell to large companies. My first ekkie was one of those. Don't get me wrong, there are, of course, excellent breeders out there too. The reality is that tracking parrots by leg band numbers is more often than not a fruitless effort. Wish I had better, or more helpful news for you.