Downloading The Sims 3 Seasons expansion pack.

What is your base game version right now ?

To find out, open your launcher and hover over the little base game icon in the lower left part of the launcher. It should say 1.42.

More Details can be found here: http://sims3.crinrict.com/en/2011/01/tutorial-how-to-find-your-game-version.html

For Macs: http://bluebellflora.com/ts3-on-a-mac/checking-which-patch-version-youre-running