To get a copy of your GED certification from Berrien County, Michigan, you'll need to contact the Berrien County Intermediate School District (BCISD). They are the entity that administers the GED testing in that area. Their website is your best starting point. Look for a contact page or a section on GED testing or transcripts.
If you can't find the information online, call them directly. They will likely have a process for requesting a copy of your certificate, which might involve providing identification and potentially paying a fee.