The method to get version 1.45 depends on whether you want the latest version or specifically need to "downgrade" to this older version for mod compatibility. Legacy Updates - Euro Truck Simulator 2
You can download the Free Trial directly from the official website, though the full version requires a Steam Key. Key Features of Update 1.45 Euro Truck Simulator 2 Version 1.45 Download
Several mechanical and quality-of-life updates were included: ETS2: Update 1.45 - The Truck Simulator Wiki The method to get version 1