MAC PRO 6,1 late 2013 what firmware is this

That version of firmware is rather old.

You should consider finding can old external drive and installing 10.14 Mojave on it, which should install at least 127.0.0.0.0 before it installs Mojave. Bringing 10.14 Mojave up-to-date after that firmware in installed might update to version 131.0.0.0.0

NOTE that firmware is NOT installed on the drive, but on the private store on the processor card.

"Find a drive, any drive above about 50 GB will do.

ERASE the drive with Disk Utility and Create a GUID partition Map, MacOS extended, journaled (HFS+) Volume on it.

Give the drive a distinctive name different from Macintosh HD so as not to be confused later.

use this article to obtain Mojave download image, but NOT using Recovery (whose options are too limited):

How to download and install macOS - Apple Support

follow directions but specify the "Found" drive as the destination.

it may tell you a firmware update is required.

it may tell you a special procedure is required, if so, PRINT the directions.

proceed to install.once completed, create a new Admin user just for this system, and do NOT import files.

apply all software updates.

check the firmware version now.

you either skipped ahead several versions and missed the firmware updates on the front, or cloned MacOS onto that drive from a different Mac.

The requisite firmware is supplied the first time you go to install MacOS. In this case, Mojave. But you can do that install to ANY drive. I recommend you find a spare drive, as MacOS will not install older over newer, and you don't need Mojave on your internal drive.

"Find a drive, any drive above about 50 GB will do.

ERASE the drive with Disk Utility and Create a GUID partition Map, MacOS extended, journaled (HFS+) Volume on it.

Give the drive a distinctive name different from Macintosh HD so as not to be confused later.

use this article to obtain Mojave download image, but NOT using Recovery (whose options are too limited):

How to download and install macOS - Apple Support

follow directions but specify the "Found" drive as the destination.

it may tell you a firmware update is required.

it may tell you a special procedure is required, if so, PRINT the directions.

proceed to install.once completed, create a new Admin user just for this system, and do NOT import files.

apply all software updates.

check the firmware version now.