Conformity Announcement

Dear Apple

My name is Viet, currently living in Vietnam. I have a friend who lives in the US, and I asked him to buy an iphone 12 pro max for him, but when we sent it back to Vietnam, customs in Vietnam requested a certificate of regulation (Certificate Regulation or Conformity Announcement). I don't know how to get it, can you help me? I am very worried because I might lose my phone if I don't have valid documents. Thank you