I don't have that particular model, but on all my Samsung devices the Screen Record is in the Nav menu when you swipe down from the top of the screen (swipe all the way down).
If it is not in your Nav Menu then click the settings icon in the top far-right corner (three dots) and tap "Edit buttons". That will bring up the nav menu icons that are in reserve on your phone. Screen Record should be there among the greyed out icons, then just drag it into your Nav Menu where you want it and press Save.