after format  

If drive E was online during the attack on drive C, then very likely, drive E was also attacked and is just as bad off as drive C.

@Bree has already given you the instructions that are available, Twice, These may work if the malware was an old version, if it was a newer version the decrypt instructions will not work and it's likely that your files are not recoverable

Long, years, before Ransomware ever reared it's ugly head, we had some pretty nasty viruses.
Heck, we even had them back in the 80's, when DOS was the default OS. And we removed them with an anti-virus program on a 3.5" Floppy Disk.

Since then, how many thousands of times have we posted to "backup your HD", or at least your personal stuff, to some external media that a virus can't reach. And don't just do it once and then forget it....like so many do. To be any good, a backup must be as recent as the last data files you saved to your HD.

Practicing what I preach, I backup all my data files almost daily, and my C: drive weekly, and I clone my entire SSD drive every two weeks, to a 1TB internal drive, that is only connected to the motherboard during the clone process, and then it's disconnected for safety. The worse virus ever, cannot infect a drive that is not connected to the motherboard.

So, if something bad happens on my C: partition on my main SSD, I have data backups, C: partition backups and even whole SSD clones.

I do sympathize with someone who has lost everything, because I see it often, but when it's GONE, it's GONE and there ain't a dang thing I, or anyone, can do about it.

Sorry, I just had to get that off my chest.

TM

In theory, if ransomware exists anywhere on a computer, if it kicks in during a backup, then both the source and target HDs are vulnerable. That's why several sources suggested having "air space" between 2 or more backup HDs.