How to get the DC power I need
The instructions on the page you cited clearly states (in BOLD type):


  You must use a 5V DC power supply to power these strips, do not use higher than 6V or you can destroy the entire strip.


While you connect the data control line in series (or in parallel to each shelf depending on what kinds of patterns you want to create), you must connect the power to everything in parallel. That means that a 5V supply operates everything. The controller (Arduino, RasPi, whatever) plus all of the LED strips. The page also states that 2A per meter (or per-shelf in your case) is probably a reasonable average to use for specifying a power supply. So a 5V, 20~30A power supply would be suitable for your project.  

A single power supply would be more convenient than a bunch of separate supplies. But either would work.

This is one of my favorite vendors of power supplies, but there are many sources including Amazon and Ebay. Here is a whole page of 5V power supply options:  http://www.mpja.com/5-Volt-Power-Supply/products/534/