This thread's last reply is from May 22, 2021, 5:33 AM UTC. Software, malware, and removal-tool
advice below may be out of date — treat specific steps and download links with caution.
Gary R
You have been infected with one of the STOP Ransomware variants .... https://www.bleepingcomputer.com/forums/t/671473/stop-ransomware-stop-puma-djvu-promo-drume-help-support-topic/
The experts in dealing with Ransomware are located at the link I've provided above.
From what I can see the nusm version is one of the more modern versions, and as far as I'm aware there is no decryptor available for it at present, but it is possible that one has been developed that I do not know about, so I strongly recommend that you post for help at Bleeping Computer, and get the advise of their decryption experts.