Get the game legitimately on Steam and use the beta branch if you really need that version.

To download and install Euro Truck Simulator 2 (ETS2) Version 1.38

The AI cars got new engine sound samples. You can now hear the difference between a small city hatchback and a muscle car passing you on the Autobahn.

Downloading Euro Truck Simulator 2 V1 38 is a straightforward process. Here's a step-by-step guide: