The SKS in its true configuration is a internal 10 round fixed mag weapon, Utilizing 10 round stripper clips. There was a variation that Norinco made to side step the first ban that put a crappy thumbhole stock and a detachable AK 5 round mag on a 16" barreled SKS . Had one and highly recommend it. The Original SKS though will need the fixed factory mag removed to use a high capacity mag ( removing it is easy and part of the break down to clean process) , The high cap mags that work for the SKS are NOT AK47 mags , the ones that work look like a AK mag but will have a 2-2.5" metal lip that will extend out from the top front of the mag to engage the frontal location that the original mag locked into. Just so that you know and walk into it informed
Now I'll touch on the other side of this coin for you since in Canada you are pretty much in the same boat as people in a number of heavily regulated states here in the south. While the 30+ round magazine has appeal to it especially to someone that hasnt been able to have it before. There are some pros and cons to it . First it is awkward to lock into place with any kind of consistency , Some of those high cap mags have been known to have unreliable feeding .
Now the Stripper clips i mentioned should be available to you up north. When the last round is fired the bolt will lock open and at that point you'll notice the "C" shaped groove in the front top of the bolt that alignes the clip and the 10 rounds it holds into position and with the thumb or webbing of your hand, They pop right into the Original mag and bo0m off to the races .
The advantage you have with the stripper clips and original box mag is :
1) that it isnt gonna get you busted , that to me is pretty important.
2) you can actually maintain a pretty steady rate of fire with the original set up , as our american boys found out in Vietnam ( the sks was abundant there and proved its stopping power and reliability in the mud the blood and the guts of combat) The reliability of the SKS is well known and the high capacity after market mags can be hit or miss.
3) the stipper clips cost on average 10 cents or less depending on where you find them , Heck I have seen people here trading them before. They are considerably lighter and will work with your weapon as designed for military combat purposes
Like I said just want you to go into it informed, this is all ground I covered a number of times . Good luck with it and be safe.