Trying to monitor mount points on Windows server

Question

I need the script below to be able to display in this format(bolded):
Data:
Instance1        value1
Instance2        value2
InstanceN        valueN
The 2 big issues I'm running into is getting the results of $freespacegb to display on the next line after Data:.  Secondly, I need the 2 columns from the results in $freespacegb to be separated by a tab (aka 8 character spaces).
Here's the script I'm working with so far: 
if($args[1] -eq $null -or $args[2] -eq $null)
Write-Host "Message: Credential not given";
exit 1;
$deviceName = $args[0];
$username = $args[1];
$password = $args[2] | ConvertTo-SecureString -asPlainText -Force;
$credential = New-Object System.Management.Automation.PSCredential($username,$password);
$freespacegb=gwmi win32_volume -ComputerName $deviceName -Credential $credential | ft -HideTableHeaders driveletter,@{l='FreeSpaceGB';e={$_.FreeSpace/1024MB -as [int]}}
Write-Host "Data:";
$freespacegb
Any assistance with this would be greatly appreciated

Answer 1

Thanks very much for your help
Here's the script now after your suggestions:
if($args[1] -eq $null -or $args[2] -eq $null)
Write-Host "Message: Credential not given";
exit 1;
$deviceName = $args[0];
$username = $args[1];
$password = $args[2] | ConvertTo-SecureString -asPlainText -Force;
$credential = New-Object System.Management.Automation.PSCredential($username,$password);
$freespacegb=gwmi win32_volume -ComputerName $deviceName -Credential $credential | ft -HideTableHeaders driveletter,@{l='FreeSpaceGB';e={('{0:N2}' -f ($_.FreeSpace/1Gb))}}
Write-Output Data:(write-output $freespacegb)
Here's what the results look like now after I run the script:
Data:
C:                                                                                            13.48                                                                                        
D:                                                                                            16.45                                                                                        
F:                                                                                            289.84                                                                                       
E:                                                                                             0.00                                                                                         
G:                                                                                             105.04
Any additional help you could provide would be great