I want to save one of my Yahoo E-mail folder on my PC, because I have oversees trip.?

It used to be, under Mail Options for Classic mail, that you could export a folder and you'd get a zipped filed full of messages in .eml format to download. I see that Classic Mail options are gone, now, and there is no Export that I can find in the Plus options. Looks like you may have to hunt down the hidden page where you can ask for support and ask there. Good luck with that.