Place your cursor at the top left of page 38 and wipe down to the top left of page 39 to highlight all of page 38. Use Cntrl-X to cut the page and then place your cursor at the top left of page 5. Use Cntrl-V to insert the page as Page 5. Save Document.
It might be an idea to work (practise) on a copy of the document in cast it all goes t*ts up.