Your Early 2013 systems SSD sadly won't work in your Mid 2015 system as it is using a mSATA interface.
The Late 2013 model also won't work even though it has a PCI2 x2 interface as the firmware on your older SSD won't work in the newer system. Besides, your newer system has a PCIe 2.0 x4 interface which is more powerful than what the older drive can interface with.
The best you can do here is get an external case to hold your old drive. Here is your options: OWC - SSD Upgrades for MacBook Pro with Retina Display Models. What I would do here if you are planing on selling your old system is get a smaller replacement drive and case setup and then swap out the drives so you have your bigger SSD with your stuff on it mounted in the USB case.