It looks like "Farm, Powder--Laurel-Bowie LONG (27.72 mi.)" will be a good practice ride for the columbia triathlon ride. It has about 200 ft. elevation change, but a couple more hills. The columbia one has about 300 ft. change.
The ride to westminster might be a good train up too, it says it has a 1000 ft. ascent. So it would be good for hill training. Then see how long it takes you to do the powder mill road ride.