Without understanding what you are trying to do or why you are looking to export passwords I don't think your question can be answered.

I would like to export my passwords from Firefox on my PC (which I can already to) and import them into my Android Firefox.

No replies, really? This is a simple question - how do I export my passwords from my Win browser into my Android browser?

I was traveling.

What you want to do is impossible. The file formats are not the same on Desktop and Firefox for Android. In addition access to the user profile is on protected storage on Android which is impossible to view unless your device is rooted.

The supported way to do this is to use Firefox Sync. https://support.mozilla.org/en-US/kb/how-do-i-set-up-firefox-sync

I have been using Sync for a long time, but it has never synced passwords - only bookmarks, etc. I appreciate the info, though, that want I want to do is impossible.

Ok. So this makes sense. The password manager only works for the exact site that set the password. If the website redirects to m.example.com and you have a password set for example.com the password is not shared.

You could go to the mobile site m.example.com for example and login to that site. This might require you to change the 'User Agent' to a mobile one on desktop.