Hallo Cielloickoi49
Your request is a bit vague for specific recommendations…
While Mürren is indeed an interesting place, accessing it is rather complicated due to several different (slow) means of transportation, therefore it’s taking ages to get there or out of there. Making it a rather unsuitable base for ‘exploring Switzerland’ by train in case you had this in mind, despite of its quite central location within the country.
So if staying in Mürren, better remain in the vicinity (by Swiss standards, meaning the same or an adjacent valley 😊), as there’s already more than enough to do and see in that surrounding area. Albeit minding the weather conditions and short-term forecasts, so remain flexible.
A Swiss Travel Pass for a few days helps saving money only if traveling a lot every day in terms of longer distances. The similar Bernese Oberland Pass (+ separate tickets for those not covered stretches from/to Zurich) MIGHT make a little more sense in your case, as in that area it’s fully including more (expensive) touristic cableways / railways to summits than the STP. Such as the Schilthorn right above Mürren.