I don't seem to see an option for Dropbox for Linux 16 Mint Petra. Would the others, like Caja still be OK? I am pretty new to this so please answer with full instructions if possible, thanks a million.

Where are you looking for "an option for Dropbox"? If you have an account with them you just log on using your browser. What Email client are you using? Thunderbird? Something else? How about telling us how you used to access Dropbox before switching to Mint.
jdk

Just so you know Mint 16 ended support July 2014. If you upgrade / re install to 17 you should be ok for 5 years. 17 is a long term support version, 16 was not.

That being said. Goto dropbox.com > download. Download the proper .deb for Ubuntu. When downloaded (i think this works in mint) double click the downloaded deb, your package manager should take over from there... it will require your sudo password to finish. That will install the dropbox client to your computer.

I have used Dropbox for years, but I gave up automatically loading my docs file as when travelling it made things difficult. Now my Dropbox account doesn't seem to have an auto upload option?

I have Linux Mint Petra. I am in Nepal so I don't want to shift everything as electricity unreliable. I can do more when I get to Laos.

I tried using Software Manager but no Dropbox programme specific to Linux Petra. But maybe the general one for Ubuntu would work? I want to be able to auto download when I want and then switch it off when not. DOes all that make sense - I love Linux and several friends now use it as I showed them. Thanks

Graham