Pixel and Nexus will be the first devices to receive Android Security patch every month. Samsung has gone ahead and released the security patch for the April month for Galaxy J3(2017), before Google has released official details of what that patch entails or rolled it out for its Pixel phones.
Currently Galaxy J3(2017) units in Netherlands and Luxembourg are getting the April 2018 security patch. Still there is update on vulnerabilities the April patch will fix. Update can be checked manually through settings–> software update. Update will take time to hit all devices across the globe.