Click on File, then Export, select messages....you can then export them to a file and there are a number of options as to the format you put them in. This file can then be imported.
i did this recently to get emails off my old PC and onto my new one, copying the file I created onto an external hard drive, of course as they were compatible from Outlook to Microsoft Mail (which replaced it) I could save as a .pst file (personal folder), you may have to do it as comma delimited or something else.