Hello Shuelogheass77
Are ypu tourist or Swiss resident?
Are you talking about the SwissPass or the Swiss Travel Pass? With the latter you cannot buy online tickets, only at the ticket window of the cable car in Zermatt.
The SwissPass Card ID is only known once it has been delivered to your place.
In my opinion, it makes little sense to buy mountain excursion tickets in advance as you will not know the weather forecast. It might be that you end up in the clouds while you paid a fortune to get there.
Kind regards,
Roland