If someone can please advise how I copy the iTunes playlists that I have created on my iphone onto my PC ?

See Recover your iTunes library from your iPod or iOS device - Apple Community. There is a script there that can recreate the playlists in iTunes as long as the songs are in the library. If needs be there is advice on copying over the media too. An alternative approach is to take a subscription to Apple Music which should allow playlists on your device to sync to your library over the air. If you do that make sure to download all the non-Apple Music content to your library and back it up before closing out the subscription.

tt2

If you have your iPhone set to Sync with iTunes, the playlists created on the phone should be copied back to your iTunes Library automatically, but note that if you left the Playlist as the default name created on the phone, it might get changed by iTunes, especially if the same list name is already in use in your Library.

If you are managing your phone by using Manually Manage then those playlists will not be automatically copied back. I assume (since I've never tried it) that you can drag the playlists from the phone into iTunes.