If you still don’t have a content database to move site collection, you need to create it. You can do it via SharePoint Central Administration or via PowerShell. Your account must be at least dbcreator role (better db_owner).

New-SPContentDatabase -Name ContentDbName -WebApplication WebApplicationName

 

For example

New-SPContentDatabase -Name SPDEVContentDBTest -WebApplication "SharePoint10 - 80"

 

To see a list of Web Applications of you SharePoint, use command:

Get-SPWebApplication

 

To see a list of Site Collections in your SharePoint Web Applications, use this code:

$url = http://sp10dev
$webapp = "SharePoint10 - 80"
Get-SPWebApplication $webapp | Get-SPSite | select id, url