Do you mean you did OCR to the original, so you have a Word text file?
(If what you have is a graphics file, you can't do anything with it in
Word.)
Your OCR application likely has a setting for "Preserve format?" or
something similar. Assuming it understands that the columns are to be
read sequentially, choose "No" for that option.
(I used to have an OCR program where you had to drag text boxes around
the parts of the preview page to tell it what order to scan in, but if
a page has a simple two- or three-column format, maybe it does that
all by itself these days.)