Here is the situation. I connected my iPad to some new PC, Synced, then ticking Sync Apps from Devices->Apps will give me warning that all existing apps on my iPad will be replaced with those from Library->Apps. But in Library I have just couple old apps, which long time ago I used. So how I can sync the library in iTunes with my existing apps from iPad?

EDIT: I have tried to click on Transfer Purchases, but not all of the items went to the library, just few of them.