If it is an automatic it could be a C-6 or it could be an AOD. Does the "D" on the steering column sit in the middle of a white circle? If so, that stands for "overdrive" and you have an AOD. If not, you have a C-6 which is a thre speed. Most likely you have a C-6.
I envy you living in Troutdale. The Gorge is my favorite place to go on vacation. It is beautiful down there.