The formating would normally be controlled in Settings/General under the "store currency" section:
It may also be controlled under "Theme Settings" when editing your theme in Online Store/Themes/Customize.
If neither of those areas controls how the price appears, then the pricing is likely controlled by the app. You'll want to look in the apps admin to see if you can update how the pricing appears or reach out to the app developer for further support.
Let me know how that goes.