Adding a "prefix" to page numbering in Word

[Becky]

I'm working on a document with several files. Each document should have its
own page numbering to correspond with the chapter number - 1-1, 2-1, 3-1,
etc.

I do not want to use the chapter number (which requires outline numbering)
formatting. I only want to tell Word that "1-1, 2-1, 3-1" are page numbers
in the footer. This is possible within WordPerfect, but I've been unable to
find a solution in Word.

Does anyone know how to add a customized "prefix" to page numbering in Word?

Thanks in advance!