App, RootStack, MainTab순으로 수정하겠습니다.

App.tsx

import React from 'react';
import {NavigationContainer} from '@react-navigation/native';
import RootStack from './screens/RootStack';

function App() {
  return (
    <NavigationContainer>
      <RootStack />
    </NavigationContainer>
  );
}

export default App;

screens/RootStack.tsx

import React from 'react';
import {createNativeStackNavigator} from '@react-navigation/native-stack';
import {RootStackParamList} from './types';
import MainTab from './MainTab';

const Stack = createNativeStackNavigator<RootStackParamList>();

function RootStack() {
  return (
    <Stack.Navigator>
      <Stack.Screen
        name="MainTab"
        component={MainTab}
        options={{headerShown: false}}
      />
    </Stack.Navigator>
  );
}

export default RootStack;