Hey @Panagora ,
The location that line items are stocked at won't be available anywhere on the order itself. At the moment you can get the potential locations that an item is available at using these steps outlined here. This won't tell you which location a line item was allocated from though, because you can use any location for a fulfillment and we'll deduct the inventory from there instead regardless of where the inventory is currently allocated from. Essentially, we don't tell you which location to use - we tell you which ones can be used, and then you make a choice.
However, with our new Fulfillment Order API that is coming I believe there is some functionality in place to improve upon the current workflow.