iCloud account breach. What to do?

Hi, my iCloud account was breached yesterday in the following manner : someone managed to activate the two factors authentication of my account and link it to a phone number unknown to me. I was able to correct the situation but it took me a few hours to be able to react as I am currently traveling in Japan with « just » my iPhone and iPad. No computer.

Basically this means that someone managed to break my strong password and accès my iCloud data and files. The possible implications I foresee is

1. They stole some files and or data for ransom
2. They encrypted some files but I have tm backups
3. They uploaded some malware/ Trojan horse or whatever evil stuff they do in my iCloud files.

Number 3 scares me the most. How can I scan my online iCloud files for malware ?

what would be the proper reaction to what happened ? Off course I already changed my password for something I cannot even remember and linked the 2 factor id to my phone.

Thanks for your help.

Vania