I need to get all the files including the files present in the subfolders that belong to a particular type.
I am doing something like this, using Get-ChildItem:
Add | select FullName to the end of your line above. If you need to actually do something with that afterwards, you might have to pipe it into a foreach loop, like so:
| select FullName
get-childitem "C:\windows\System32" -recurse | where {$_.extension -eq ".txt"} | % { Write-Host $_.FullName }