This is the guide to check "how many orders are from mobile app".
You can see "total sales from mobile app" on
Shopify Admin > Analytics > Dashboard > Total sales
2. You can also check which order are from "mobile app" on each order history.
Shopify Admin > Orders
3. If you want to filter orders from mobile app, you can filter using "sales channel" on Orders.
Shopify Admin > Orders > More filters