Visual Upgrade All SharePoint Sites in a web application using PowerShell

##### Visual Upgrade All SharePoint Sites to 2010 version in a Web Application #####
 
$SPwebApp = Get-SPWebApplication "https://migration.company.com"
 
    foreach ($SPsite in $SPwebApp.Sites)
    {
       foreach($SPweb in $SPsite.AllWebs)
        {
         
           $SPweb.UIVersion = 4  #set it to 3 if you want SharePoint 2007 look and feel
       $SPweb.Update()
    write-host $spweb.url
        }
    }
read-host  #just to pause

$webapp = Get-SPWebApplication <web-app-URL>
foreach ($site in $webapp.sites)
{
   $site.VisualUpgradeWebs() 
}