Never knew there were comics. Where would I get them?

I get them at my local comic shop. Dark Horse is the publisher if toi need to order online.

Buffy continued with season 8 in the comics (They are considered canon).
It's currently on season 10 which they a dit would be the last season.
I'd try
www.tfaw.com
or
amazon.com

The précédant poster's suggestion for tfaw.com is a good one. I've bought many comics from there. Another good option is Comixology.com if you'd prefer to buy digital versions rather than paper copies. It's a bit cheaper that way.