I have content database from SharePoint 2013 which is down
I setup another SharePoint 2013 I have only content databases
how can I restore this content database to new SharePoint server 2013
If those WebApplications are installed on the same farm, you might not to have to consider testing database before mounting it to new WebApplication. If not, you have to test database before mounting, since you might miss dll or wsp, etc on the new farm.
Test-SPContentDatabase -name databasename -webapplication http://servername > C:\\dbtest.txt
You can find erros from log file and resolve it if necessary. Then, you the mount command:
Mount-SPContentDatabase databasename -DatabaseServer "myDbServer" -WebApplication http://servername
The best solution is the export the .bak from the old SQL Server, then import it to the new SQL and then mount the contentDB the to new web application.
Mount-SPContentDatabase "MyDatabase" -DatabaseServer "MyServer" -WebApplication `http://sitename`