...can’t find the file at .../phpmyadmin/export.php

To export use this command:
mysqldump -u USER -p PASSWORD DATABASE > filename.sql

To import database from dump file (in this case called filename.sql) use:
mysql -u username -p password database_name < filename.sql

https://www.knownhost.com/forums/threads/phpmyadmin-database-export.2649/