When the Kaaba was built, how were people worshiping Allah?

I understand that Ibrahim and his son Ismail build the Kaaba but how was worshiping Allah like? I ask this because the Kaaba was built before the Quran and before the rules of the 5 prayers were submitted to people. Did they used to perform Umrah? But doesn't Umrah require the 5 prayers? Sorry for not knowing about this topic (I am still reading on Islam). Thank you!