Sadly, you destroyed the data by repartitioning the drive.
Had you just plugged it in and assigned the drive a letter, you would have been ok. Repartitioning the drive makes the data generally unreadable. Now there are ways to get to the data again, but your looking at a lot more in depth work (with specialized tools) than your average user can do. If the data is truly critical, find a shop that does hard drive forensics.
I wish I had better news for you.
