Z390 Pro 4 M.2 drive not showing in BIOS

Hi Am new here
I have been unable to find a URL with an
Z390 Pro 4 mother board bios update.
I have looked for hours Thanks Vic

Hi Vic, it's highly unlikely that your issue is BIOS version related but you can
find all the available BIOS versions for your board here:
https://www.asrock.com/MB/Intel/Z390%20Pro4/#BIOS

Before you go down the update route however try the following:

1. Make sure the M.2 drive is properly seated in it's socket.

2. Go into windows (assuming you have another boot drive installed) and check
in "Disk Management" to see if your drive is showing there.
a. Open Disk Management: Right-click the Start button (or press Windows Key + X)
and select Disk Management.
b. Initialize the Drive (if new): If the drive is brand new, an "Initialize
Disk" window will automatically pop up. Select GPT (GUID Partition Table) as it
is the modern standard, and click OK.
c. Create a Simple Volume: Look at the bottom of the window for your new disk.
It will be marked with a black bar indicating "Unallocated" space. Right-click
this unallocated space and choose New Simple Volume.
d. Specify Volume Size: The wizard will guide you; click Next. You can specify
the size in megabytes (MB) or leave it at the maximum default to use the entire
drive.
e. Assign a Drive Letter: Click Next, and assign your preferred letter (e.g.,
D, E, or F) to the drive.
f. Format the Drive: Select NTFS as the File System, leave the Allocation unit
size to Default, and give the drive a name in the "Volume label" box (e.g.,
"Media Drive"). Ensure Perform a quick format is checked.
g. Finish: Click Next and then Finish. The status will change to Formatting,
and it will then be accessible in File Explorer.

3. If it is the only M.2 drive in your system make sure you install it in the
top slot. The bottom slot shares resources with some of your SATA ports so if
you have SATA drives connected it can conflict and not show up in BIOS/the OS.

4. Under "Boot options" in your BIOS make sure CSM is set to disabled. Most NVME
drives require this setting to be disabled. CSM = Compatibility Support Module
and it exists for old, legacy hardware. Almost no one uses any hardware that
needs it anymore.

Good luck.