I'm glad it helped.
Moving content around devices has always been challenging when using iTunes under Windows (any version).
I had many failed attempts until i decided to give up control and allow iTunes to manage all my content. Once i did that, It was pretty simple to back up an old device (like your iPad gen 1) and restore to a new device (like your iPad Air).
Before the BACKUP, be sure to "Transfer Purchases" so your Windows system is fully loaded with the old content. With this approach, when you restore to the new device it will load apps and content from iTunes instead of requiring re-download. This was also successful in restoring progress on apps, like Candy Crush, that required more work when i did the iCloud backup/restore.
I have switched to iCloud backup/restore, which requires re-download of all apps, and works a little bit differently, if i'm not mistaken. It's been a year so, i apologize if this informaiton isn't correct.
For the record, i use my work computer for iTunes. My company backs up our computers automatically and limits storage capacity. The default directory used by iTunes was one of the directories backed up and my content was beyond the allowable storage, so i had to switch to a custom directory, which is why I didn't allow iTunes to manage my content. It worked, but periodically iTunes major release updates would "reset' the default directory back to the Apple default, and my content wouldn't get moved and it was a hassle for me to straighten it out. iCloud solved these issues.
