How to store and retrieve contacts Samsung Galaxy Express 3 J120A?

Hi,

I have a Samsung Galaxy Express 3 J120A and would like to be able to store the contacts information online, and update it when I want to or have it do it automatically however that would work, and then be able to load it onto another phone when I want to. Can anyone tell me how to do that or suggest a tutorial explaining how to do it? I have more than one of that type phone and want to move the sim card from one to another to get familiar with and practice doing things like this. Also hopefully to use one phone for a few weeks and update it, then do the same with another, and then a third, and then go back to the first one and hopefully it will retain some of the info so it will only need some updating... Will that work? Also there's a micro SD card I plan to move along with the sim card. Service is with AT&T if that matters much.

Thank you for any help learning this stuff!

David