Both the .ab65 and .alb5 files are documents from Adobe PageMaker, albeit from different versions of the tool. It has been discontinued years ago, but perhaps some users still use it on old computers, typically people that prefer older, more simple software. You will have to acquire specific version of PageMaker in other to achieve this kind of ab65 to alb5 conversion, or to at least export the content to some exchange format.
Updated: August 4, 2023