I replaced Windows with Ubuntu, but when I log in into Ubuntu, the drives (partitions) are not to be seen, and there are important files on my drives.
Windows was installed in
C:\. I need the other drives so that I could recover the files.
If you set during installation Replace Windows with Ubuntu, than all the files on your system were deleted.
You can try use some data recovery programs but you may not succeed to recover all of your data.