How to transfer contacts, pics, music and apps "FROM" iPad to desktop computer?

You can copy your iTunes purchases (apps, music etc) over to your computer's iTunes library via the File > Devices > Transfer Purchases menu option.

For photos taken with the iPad (or copied to it via the camera connection kit and/or saved from emails/websites) then they are copied off outside of iTunes : Import photos and videos from your iPhone, iPad, or iPod touch to your Mac or Windows PC - Apple Support

For your contacts, are they not stored on an email account that you have set up in Settings > Mail,Contacts, Calendars ? If you have more than one email account set up with contacts enabled on it then any new contacts that you've set up on the iPad should have been stored in the account specified in Settings > Mail, Contacts, Calendars > Default Account (that setting only shows if there are multiple accounts with contacts enabled). They should be accessible on that email account e.g. if accessing the email account via a browser