How to create a p12 cert file, mobileprovision, & p8 cert file to deploy to app store

Greetings Everyone,

I have a paid Apple developer account and I want to send my Expo app to TestFlight so I can deploy it to the Apple app store. I created the p12, p8, and mobile provision files through the iTunes website, but when I try to create an ipa file through Expo, I’m given an error that says Standalone Build Failed. Is there any way that I’d be able to fix this?