I don't have access to powershell on linux but I think the syntax would be

(ls).Count

(where ls is an alias for http://ss64.com/ps/get-childitem.html which returns .net FileInfo objects, it can also return info for registry paths)

and

ps | ?{ $_.Name -eq 'tobekilled' } | %{ $_.Kill() }

(ps an alias for http://ss64.com/ps/get-process.html returns .net Process objects)

or the equivalent of pkill

Stop-Process -Name 'tobekilled'