Updating the Cordova version requires you to edit the platforms.js file found in:
You can change the version individually for each platform, tho I suggest you use the same version for all.
Also, it might be the case you’re looking to update only because of the Google Play warning regarding the high severity cross-application scripting (XAS) vulnerability found in Cordova 3.5.0. If so here you have the file updated to point to version 3.5.1 which fixes the mentioned vulnerability: platforms.js.
Note: In case you are using CTP 1 of the Hybrid Apps the path will be different: