MacPro 5,1 victim of malware zero day Bob I could use some wise council?

I fell victim to December Zero Day Cyber Attack.

That would be incredibly difficult to have happened since that particular malware is a Windows only threat.

I'm not sure how you managed to do it, but if you used Disk Utility to erase the drive, and chose the far left physical drive name, then you also erased the hidden recovery partition.

The firmware for a 5,1 Mac Pro doesn't support booting to Internet Recovery Mode, so you can't do that. If you have no bootable drive at all, then you'll have to follow these steps.

Put a hard drive into one of the Mac's empty bays and install Snow Leopard from the gray disks the Mac shipped with. You must do this since Snow Leopard has no clue what an SSD is and won't even list them as a choice to install the OS. From there, update SL to at least 10.6.6 so the App Store gets installed.

Upgrade from Snow Leopard to El Capitan. You can then download the full Mojave installer and create a bootable Mojave, USB drive. Boot to the USB drive and install it to the SSD. You can then remove the hard drive from the Mac.

Command-R boots recovery from your internal drive. Since you deleted your startup disk you cant’ do that.

Option-Command-R boots recovery from the internet instead. Hopefully you have a reasonably fast internet connection. Hopefully you have backups of your important data too.