First, I typically test code like this in “log output” so I don’t mess up my shop data and I can see the variables.
A fulfillment service on a lineItem is one that stocks that particular product but not the one used for the order. Also this is deprecated, so I don’t recommend using it at all.
If you want to know which location it was assigned to be fulfilled from, that info is on: order / fulfillment orders / assigned location
Note that fulfillment orders are assigned after an order is created, so you cannot use “order created” as the trigger (reliably, unless you add a wait step after it of ~ 10 min). Better to use “fulfillment order ready to fulfill”.