Once you have the version, you need the mods. Using modern mods on 1.39 will crash your game. Here is the "Best" load order for 1.39:

Euro Truck Simulator 2 (ETS2) is a popular truck simulation game developed by SCS Software. The game offers a realistic driving experience, allowing players to explore Europe, complete cargo delivery missions, and manage their own trucking company. Version 1.39 is a significant update that brings new features, bug fixes, and improvements to the game.