Steam will automatically download the files for version 1.39. Method 2: Legacy Non-Steam Version
The 1.39 update for ETS2 brings Iberia DLC prep, new truck features, and road improvements. Here’s how to get it safely. Euro Truck Simulator 2 V1-39 Download
Version 1.39 also focused on the "behind-the-scenes" story of the simulation: Steam will automatically download the files for version 1