used here https://medium.com/@themukeshsolanki/demystifying-datastore-a-comprehensive-guide-to-using-datastore-with-jetpack-compose-d89c813232d7

ProtobufDataStore.kt

// Define a DataStore 
val dataStore: DataStore<UserProfile> = context.createDataStore(
    fileName = "user_profile.pb",
    serializer = UserProfileSerializer // Generated serializer class
)

// Function to retrive the user profile
override suspend fun getUserProfile(): Flow<UserProfle> {
  return dataStore.data.map { protoBuilder -> 
    protoBuilder
  }
}

// Function to store the user profile
override suspend fun saveUserProfile(userProfile: UserProfile) {
  dataStore.updateData { store -> 
    store.toBuilder()
        .setUserProfile(userProfile)
        .build()
  }
}