I've answered my own question:
https://homeownersolutions.toro.com/...ualsResultPage
You may have to enter the 38381 model number...
The Toro uses two belts: the first one is toothed and steps down about 1:3, and the second is a multi-vee groove with a tensioner, which further reduces the speed by about 1:6 or 1:8. The belts are on the left side as you stand using the machine.