You'll need the serial number, so that's good that you have one. You'll also need a bill of sale, so get one, it doesn't matter how or where, just get a bill of sale and act confident about it. The registration bureau will ask you to get an 'out of province mechanical inspection', so be prepared for that. Do not loose your temper at any time throughout the long, tedious, frustrating, annoying, unnecessary, B.S. hoops you have to jump through, or your clerk will turn governmental on you and things will get worse. --------Don't ask how I know this.
Good Luck.