I am using PostgreSQL 8.3.13. I have a backup file of PostgreSQL 8.4.14. When i restore (Using PgADMIN III, by right clicking on database) it shows following error

D:\PostgreSQL\8.3\bin\pg_restore.exe -h localhost -p 5432 -U postgres -d aflprod "C:\Users\USAMA\Dropbox\Advance Fashion Backups\backup af 20140201.backup"
pg_restore: [archiver] unsupported version (1.11) in file header

Process returned exit code 1.

please guide me how I can restore this database backup. please I need to know easy solution as I don't have good command on database. thank you