Need help to publish/deploy new version of already existed app in Google Play

I need to publish (deploy) project created (App) and working with Expo Cli.
Project owner gave me access to Google Developer Console. I don’t know when first version of the App were deployed to Play Store, but most old in the library is dated 3d Oct. '18. After update Expo SDK to v. 36, I need to deploy new version of the app. In the project there already certificate for signing and one for uploading.
All I have only keystore password, .PEM file (for uploading?), also I can download .DER files for each certificate.
I don’t know which of options I should I select for do build - 1. Let Expo handle the process or 2. upload my own keystore. Also I don’t understand do I need to run expo opt-in-google-play-signing for generate new certificate or doing this I will lost possibility to publish new version of the App?