Unless you had your Sims swapped then your account is still linked to your old sim card. You can just put that one in and you'll be good to go. Also yes it comes with a microSD slot so you can use a microSD card to expand storage.
Hi David, You should try Goran suggestion. if your current SIM didn't fit the nano SIM slot of the LG G6, then you need to contact Koodo to change the SIM to the new Trio SIM. If everything is ok, you can keep the trioSIM as a backup.
The LG G6 in North America is a single SIM + microSD version, not the dual SIM variance.