Or use it for parts (screen, battery, etc) for another, secondhand J3...
But carrying on...OP? have you tried a factory data reset? You said it boots to either recovery (where the Factory Reset option is) or download mode, the latter of which is how you put the original firmware (assuming you know the version of Android/etc that was there before since ODIN won't flash older versions on top of newer ones) via a PC suite called ODIN.
I would try the Factory Data Reset or even 'Clear Cache' options first and retry. Often it gets buggered (like from a partially installed update, or crash) and just bootloops or freezes at the Samsung logo.
Worse case scenario, if you like the J3, I'm certain plenty of used examples exist cheap on eBay or Amazon, and then you got parts, like an extra battery (the J3 had a removable battery) or screen, or other bits.