I can recover my files?

I have 2 hard drives 2tb and i recently changed from raid 0 to raid 1 because 1 drive sometimes was not being detected and during rebuild the drive that hold my files die and now my book says if i replace the drive i can get my files back. I tried to mount the good hard drive in my pc after rebuild( or fail rebuild i dont really know) and it was just lost.dir in the folder.

It is always advised to wait till the RAID rebuild process finish to bring the RAID volume back to a “healthy” state. You can follow the below article helps you to rebuild RAID manually.