hello, i'm trying to restore my backup for my iphone but it's not working, need help please

i have backed-up my iphone to my itunes, after resetting all settings for my iphone, i'm trying to restore my backed-up files it keep asking for a password for the backup. i didn't set any password while backing up yet i'm not able to reset this function neither or remove or change or whatever it is just to get my content restored to my iphone back. need help please! thank you