Samsung Galaxy J3 SM-J320Y Bootloop Problem
It seems from what you have mentioned above, that your device was not rooted and thus there is no custom recovery installed on your device.
So here are the two methods which you can try -

Method-1 

Step-1. Power OFF.

Step-2. Press and hold Power + Volume Up + Home.

Step-3. Select "wipe data factory reset".

Method-2 

Download the stock ROM for your device and then flash it using software like Odin.
Here's the link to download the ROM- http://www.android.gs/download-stock-android-firmware-files-for-samsung-galaxy-j3-2016/

This will get your device to normal state.