How do I export email messages on Windows 8.1 computer from Windows Live Mail?

Please help: I need to back up my email messages from my pc to a usb drive . I use Windows Live Mail on a Windows 8.1 laptop. My pc is having serious problems and I need to ship it to the manufacturer and everything will be wiped out from my hard drive. I have backed up all my documents, of course, but need to back up my email messages (which have been downloaded to my hard drive) and my contacts. I have tried the steps outlined on MS community, but it doesn't work. Probably works great for Windows 7, but not for Windows 8.1. I haven't upgraded to Windows 10 yet because I'm having so many problems already and I didn't want to confuse the issues my computer is having (apparently it needs a new processor, and motherboard has already been replaced). Can anyone help me? Thanks!