Toyota Sienna 2010 Owner's Manual page 65

1-3. Adjustable components (seats, mirrors, steering wheel)
Installing the second seats
When you install the second seats, be sure to place them where the
seats are originally positioned because the second seats are not
interchangeable.
Outer seats
Front of vehicle
8-passenger models
7-passenger models
Center seat (8-passenger models)
Front of vehicle
66
You can distinguish the original
seat position by the position of
the front leg pins and the shape
of the seat striker bezels in the
floor.