Hi Hana
The S9 is a swiss train, it’s swiss tariff, although Jestetten is a German village.
You find the price here:
https://ticketshop.zvv.ch/pricefinder?0
Just type in “Zürich” and “Jestetten” in “A” and “B”.
If you buy a day pass, you need it for at least 8 zones: 40.80 CHF (“Tageskarte”)
Attention: if you have already a day pass for the whole ZVV, it’s not valid, because it’s a line between 2 traffic association. The “Z Pass Ostwind-ZVV” includes both.
You can buy it at the automat in Zurich. But maybe it’s easier you go to the counter ans ask for a day pass “Z Pass 8 Zonen” or Zurich - Jestetten.
I know, It’s a bit confusing. Let me know if you have any questions.
Wish you a good journey!
Sincerely
Gitti