The Nikon D3400 is a beginner DSLR camera released in 2016 and with minimal changes compared to the predecessor D3300. Just a Bluetooth module (SnapBridge app) has been added and the 3.5mm microphone jack has been removed. In addition, the new GUIDE mode makes it easier for beginners to get started in photography.
We generally recommend SDHC and SDXC memory cards with an UHS-I-interface and a SD Speed Class from 10/U1 or above, if you're using a Nikon D3400. More expensive UHS-II-cards do not offer any advantage in terms of speed (burst mode) or video capabilities.