Or go to school to find the corresponding teacher, because not all schools will send the files away to see if your files are still in school. If not, find out where they were put by the school when you graduated.
Generally, files are not kept after graduation, and the school may send them back to the place of origin, that is, the place where the household registration is located. If you have changed your household registration, you should refer to the location of the college entrance examination.
If you really can't find it yourself, you can also find a professional file service agency to help you check it online.