To get the all CONTENT_DB size in SHAREPOINT server(MB), Using below commands power shell commands.
Get-SPDatabase | Sort-Object disksizerequired -desc | Format-Table Name, @{Label ="Size in MB"; Expression = {$_.disksizerequired/1024/1024}} >c:\Content_DBsize.txt
The above code will export to C drive and you can change drive for your requirement.
Get-SPDatabase | Sort-Object disksizerequired -desc | Format-Table Name, @{Label ="Size in MB"; Expression = {$_.disksizerequired/1024/1024}} >c:\Content_DBsize.txt
The above code will export to C drive and you can change drive for your requirement.