Could someone tell me how to transfer playlist from laptop to mp3? Do I have to be on Premium plan to do this?
I'm afraid you cannot download Spotify playlists as mp3's.
Spotify is a streaming service, it's not meant for downloading music off it.
With Premium you can download playlists for offline listening in the Spotify client - when you have no internet available, you can still fire up the Spotify client and listen to your favourite tunes.
But to get music files you'd have to buy them from sites like Bandcamp, Junodownload or Beatport.
Hope this helps, have a nice day! :)