Well, I can't say for certain with Earth 2140 as I don't yet have it (won't get it until GOG fix the crippled AI). I'd imagine it is just the one game, though, so just a standard single game installer.
The Earth 2150 Trilogy contains:
1) Escape From The Blue Planet
2) The Moon Project
3) Lost Souls
These appear in the installer as separate games (they were all standalone games available individually when they were released on retail discs). You just make sure that the game(s) you want installed have a tick mark in the relevant check box in the installer.
Earth 2160 is a standalone game, no expansion, so it's just one game through the installer.
Hope this helps.