Pages was introduced Jan 1, 2005, and Pages v13.2 is supposed to open those older iWork '05 documents, and later iWork versions. If the document really was created in 2004, then it is not a Pages document, and might be an AppleWorks document that was incorrectly renamed with a .pages extension. No version of Pages since '09 v4.3 can open an AppleWorks document.
You might try installing the free LibreOffice v7.6.4 as it can open older Pages (and AppleWorks) documents. If it does, you can then save that content as Word .docx and then open that format in Pages v13.2. I would try this over any online converter which might make every sentence a text box and cost you hours of editing time.