To drop multiple MySQL tables, execute the following SQL in phpMyAdmin, modifying the query to replace database_name and prefix_ with your own values:
SELECT CONCAT( 'DROP TABLE ', GROUP_CONCAT(table_name) , ';' ) AS statement FROM information_schema.tables WHERE table_schema = 'database_name' AND table_name LIKE 'prefix_%';
This will generate a DROP statement that you can copy and execute to drop the tables. If the resulting statement is too long and the SQL gets truncated, click Print view (with full texts) to copy the entire statement.