Use terraform dynamic block to create multiple Azure VM disks and format drives with naming convention

Question

I have successfully used this terraform dynamic block to create X number of additional data disks in an Azure Windows VM:

      dynamic "storage_data_disk" {
    for_each = range(var.nb_data_disk)
    content {
      name              = "${var.vm_hostname}-datadisk-${count.index}-${storage_data_disk.value}"
      create_option     = "Empty"
      lun               = "${storage_data_disk.value+10}"
      disk_size_gb      = 20
      managed_disk_type = "Standard_LRS"
    }
  }

Now I need to format them using the following naming convention for the drives:

DATA , DATA 2 , DATA 3 , DATA 4 , DATA 5 ...........etc

I have the following PowerShell script but do not know how to iterate through the X number of disks created:

    Get-Disk | Where partitionstyle -eq 'raw' | Initialize-Disk -PartitionStyle MBR -PassThru | New-Partition -UseMaximumSize -DriveLetter F | Format-Volume -FileSystem NTFS -NewFileSystemLabel "data" -Confirm:$false"

I plan to use it as a vm extension in my tf configuration like this:

 settings = <<SETTINGS

    {
          "commandToExecute": "powershell -command \"[System.Text.Encoding]::UTF8.GetString([System.Convert]::FromBase64String('${base64encode(data.template_file.tf.rendered)}')) | Out-File -filepath FormatDisk.ps1\" && powershell -ExecutionPolicy Unrestricted -File FormatDisk.ps1"
    }

SETTINGS

I need the PowerShell script to name the disks as described above(DATA , DATA 2 , DATA 3 , DATA 4 , DATA 5 ...........etc) i.e it will increment as it iterate through the list of disks created.

Note: The number of disks varies each time.