I'm sorry, but your encrypted files are lost to you. When Stop ransomware installs, if there is good internet, it sends the encryption key to it's own servers (Online ID), so there is no chance of decrypting them shy of paying the malware folks.
So sorry, but we can run other scans to ensure nothing else is amiss.
For x32 (x86) bit systems download
Farbar Recovery Scan Tool 32-Bit and save it to the desktop.
For x64 bit systems download
Farbar Recovery Scan Tool 64-Bit and save it to the desktop.
Please run it and click Scan, post back with the 2 logfiles.
Use extra posts here as needed.