How can i get all my contacts back when all iCloud data has been erased by my son? Thank you

Hi Apple support team,

I'm Phuong Bien, Apple user from Vietnam. I really need your help to get back all my contacts. I have lost all my iCloud data including all my contacts, and i'm waiting a very important business call and i don't know their number. So how can i get it back? Please help me to get all my data especially for my contacts

Thank you very much

Phuong Bien