Im not able to reformat my macbook air 2004. Missing the factory passw

Apple does not sell Macs that require any sort of password protection, so someone else did that. In other words there is no "factory password". Apple would not be able to provide one because no such thing exists.

The following Apple Support document describes how to set a firmware password, and your options if you don't know what it is:

Set a firmware password on your Mac - Apple Support

... my macbook air 2004

I don't know which Mac model you have though because the MacBook Air wasn't introduced until a few years later.