The mentioned links are related to your question, you can go with the discussions, hopefully this can resolve your query.

• Error type 3 Error: Activity class {} does not exist : Error type 3 Error: Activity class {} does not exist

• Different Ways to Fix “Error type 3 Error: Activity class {} does not exist” in Android Studio : https://www.geeksforgeeks.org/different-ways-to-fix-error-type-3-error-activity-class-does-not-exist-in-android-studio/

• Error: Activity class MainActivity does not exist #17423 : https://github.com/facebook/react-native/issues/17423

• Error type 3 Error: Activity class {....} does not exist #2349 : https://github.com/react-native-community/cli/issues/2349