Did you run the Ubuntu installer? You did not explicity tell the Ubuntu installer to format the partition, did you? If you did, then I'm afraid it's going to be a long road for you.
First, do NOT use that drive any more.
You can booting a live USB or CD of Ubuntu and the use photorec
by installing the testdisk
package and running
Have fun. It's going to be hard. In the future, create a separate /home partition instead of installing all to a single partition; it can help you avoid this problem again.