I understand you're looking for The Lord of the Rings: The Battle for Middle-earth II (BFME2). It's important to know upfront that by EA (the original publisher) due to expired licensing rights with Middle-earth Enterprises. That means you cannot buy it on Steam, Origin, EA App, GOG, or other mainstream stores.

Because of this, the game is considered "abandonware" (abandoned by its publisher for commercial sale). Downloading it falls into a legal gray area, though many in the community treat it as acceptable since no legal purchase option exists.