Thanks Nelsona for answering my question. But now I have another one. So as a Canadian, I don't need to apply for H1B visa for international travel as people from other countries do? I just need to cross the border and get an I-94?Of course. The H1 I-129 is your firm's petition, so there is no fear that YOU are abandoning it by leaving US (as would be the case if you were filing I-539). This will be the case even after approval, all the way to October when your H1 will kick in. If your H1 approval comes with an I-94, it will become your status automatically on October 1, otherwise you would need to go to border to activate your H1 at some point after Oct 1, and before your current TN expires.
got you...just one more question since this is my first time dealing with H1B. If my case is approved, can I change employer but keep the H1B valid before Oct 1? I mean, can I change the employer before Oct 1 by applying a TN, just to fill the gap, and use the new TN to Oct 1. then get the H1B transferred to new employer?Correct. You did not get a TN "visa" did you? No. So you do not need an H1-B "visa", either. Because you are Cdn. Your I-94 is all you need.
And, as I said, if your approval comes with an I-94 attached (most do) then you don't need to do anything or go anywhere but stick the I-94 in your passport on October 1. You become h1 on that day.