A Microsoft app for iOS and Android devices that enables authentication with two-factor verification, phone sign-in, and code generation
Contact your school's IT or Help Desk support, since someone with Admin access from the school itself is required to reset your MFA account access in order to allow you to set that up again on a new phone.
There might be another method possible, but whomever provides your support within your school will know those specifics, which can vary from school to school.
Rob