Dan is correct with his comment on the question, see especially my answer there on how to convert an
.ab file to a
.tar and then access the contents.
.apk files (if backed up, of course) are stored in
apps/com.app.name/a/ then. But if
adb backup was used without
.apk files then (your question is a bit confusing: "I want to use it...I don't want to use it" :)
If your goal is just to get hold of the
.apk files of installed apps, you might also want to take a look at solutions like e.g. AppMonster, which allow you to get a copy of each installed app's
.apk file to your SDCard (with the Pro-Version even in Batch Mode, and automatically on each app install). You could then use e.g.
adb pull to copy the entire backup directory to your PC, and
adb push to restore it to other devices for installation with e.g.
adb shell pm install.