Adobe AcRobat Reader - "could not open" file

My Certified Apple tech recently needed to remove my old MacBook Air (13" - 2017) OS system and replaced it with a new MacOS Monterey 12.6.6. Problem. All of my files created using the old 'Pages" can no longer be opened by Adobe Acrobat Reader (which came with the new OS system) by reason quote: "Adobe Acrobat Reader could not open files 'pages' because it is either not a supported file type or because the file has been damaged (for example, it was sent as an email attachment and wasn't correctly decoded). The new OS system does not have the very convenient 'Pages' option - for whatsoever reason?

Any suggestions please as to how I can once again open those previously generated 'Pages' documents?

Thank you