There is no official digital download or "paper" (CD key) available for the original (2004) on major storefronts like Steam, GOG, or Epic Games . Because the game is considered "abandonware" by some, it is not currently sold in digital format by its original publishers.
: A classic strategy game from Microprose available on the Conflict in Vietnam Steam Store Page . Conflict: Vietnam Download PC Game
If you are looking to play a Vietnam-themed game with a similar title or style on PC, you have several current options: Modern Alternatives on Steam There is no official digital download or "paper"