Where are they stored?

I looked in asec but the files there were not apks

[m0o5]

/data/app for installed apps
/system/app for system apps

(viewtopic.php?f=413&t=357898)

Nope. I have 2 apps I purchased on the market and neither of them are in there.

[m0o5]

These are the possible locations :

/data/app
/data/app-private
/system/app
/mnt/asec

If the apks you're looking for are not there ..

[youtube]http://www.youtube.com/watch?v=cryu8bFXLJQ[/youtube]

.. make a backup of the apps with Titanium Backup (Pro).

ultamate backup, backs up every apk on your phone. you can later grab any apk in that folder and store on computer. its a great app/