Place the downloaded .scs file into that folder.

Since this is an older mod for a legacy game, it is primarily hosted on community archives and fan sites:

Features local transport companies and Soviet-era trucks. 📥 Where to Download

Popular hubs for Eastern European map mods.

Search for "18 Wheels of Steel Haulin Ukrainian Open Spaces" or "Українські простори."

📍 Make sure your version of Haulin' is updated (usually to v1.1) to avoid crashes with large map mods.

Usually found in Documents/18 WoS Haulin/mod .

It looks like you’re looking for the mod (or "Ukrainski Prostory") for the classic trucking game 18 Wheels of Steel: Haulin' .