Bests & Worsts Reviews from Amazon

I've been so excited to add more memory to my phone (Samsung galaxy s7)... transferred my videos to the sim card and... they're all lost.. error of some sort. all my recent toddler videos are gone and I have no clue how to restore it... I'm so pissed, I can't even explain. Please just go to best buy or somewhere to get a legit card, or at least back it up first before transferring anything. Even pictures I take are not opening up... I'm returning both cards.