Does the Stronghold HD come with or where can I buy the Extreme version? (Massive amounts of units)

Stronghold HD is the extreme extreme version. It's Extreme Plus.

You get massive amounts of units with the HD version (plus other nifty features).

If you're asking about the first game, then no, as it never received such an update. Crusader HD, on the other hand, comes with both the original as well as its Extreme version.

Oh shoot. Thanks for cleaning me up, mistermumbles. Yes, it's Stronghold Crusader extreme extreme.

This is the game that gives you the 10,000 units:

http://www.gog.com/en/gamecard/stronghold_crusader