If you have a phone plug it in and dial your mobile and see the number.
Or try the phone book and look up your address? www.directories.ch

ADSL providers all use the same network so it does not matter which one you choose. I would stick to Bluewin because it's the same price as others but you get the excellent Swisscom service.
After you know your number go to www.bluewin.ch and you can order online.