Decryption of partition on ubuntu

Hi, please how can I decrypt a partition on Ubuntu?
What actually happened was that, I encrypted two partitions on windows and later before installing Ubuntu, I decrypted them but it seems like one of the drives did not decrypt, now I have completely replaces windows with Ubuntu. And I don't want to loose my data
Thank you in advance.

If you decrypted that 2 partitions correctly with windows, now ubuntu should be able to mount them. Probably you encrypted-decrypted with Bitlocker, didn't you?
Why don't you try to mount them with an Ubuntu-live pen? If you can't, probably you didn't decrypted them with windows, or happened some trouble. If this is the case, now you can install DISLOCKER on ubuntu.