If you have
a site collection and want to upgrade from SharePoint 2010 to SharePoint 2013
PowerShell, then this blog will give you step–step to do this a bit
Go to Central
Adminstration, create New Site and in Select Experience Version choose 2010.
(Example: My site is Home).
The Home page is created in SharePoint 2010 as:
Open SharePoint 2013 Management Shell and Run as Administrator.
Enter command: Upgrade-SPSite
http://server/sitecollection -VersionUpgrade (for example: Upgrade-SPSite
Wait until you see the following
Then, go to your site and launch