In your code, in the file build.gradle increase the versionCode.

To export an aab file for Google Play run

npx react-native build-android --mode=release

The file will be in the folder android/app/build/outputs/bundle/release/app-release.aab

In google play, find your app, click on “Test and release/Production” on the side bar. Then click the ‘Create new release’ button at the top right.

Drag and drop the abb file into the box. Then press ‘next’. Do anything you need to do, then click ‘send for review’.