Pokemon Quest originally released for the Nintendo Switch on May 30, 2018, and later released on mobile devices on June 27. Within a month’s time, you may have spent money and progressed quite far.
Though you can transfer saved data between mobile devices, there’s unfortunately no way to transfer saved date from the Nintendo Switch to a mobile device, whether it’s to iOS or Android.
From Pokemon.com: “Please be aware that save data from the Nintendo Switch version of Pokemon Quest cannot be transferred to the mobile versions nor vice versa.”
It’s up to you to decide whether it’s worth starting over. For reference, it takes between 15 to 25 hours to complete Pokemon Quest, less if you buy the expedition packs early on, more if you don’t buy anything at all.