The first is to pass the output to the PowerShell measure-object cmdlet. Here it is in action, showing what it returned:
get-command | measure-object
Count : 994
Another way would be to just get the count property of the command. You enter the following command and it returns just the count property, which you can see below:
PS C:\> (get-command).count
Other options exist, such as using a custom variable incrementing, but the above two options are probably the easiest.