You'll need to obtain a study permit to take a bachelor degree in Canada. Yes - you can certainly try to apply for one from within Canada. However the chances of the study permit being approved if you apply as a visitor from within Canada are lower than if you apply from outside of Canada. This is because in order to be approved, you must prove you have strong ties to your home country and have no plans on remaining in Canada long term. This is obviously more difficult to prove if you are already in Canada as a visitor.
