A:Answer Please ignore the user that mentioned a micro-SD slot. This Best Buy listing is for a Western Digital flash drive. Also, iPhones do not have micro-SD slots.
A USB flash drive, like this WD model, cannot plug directly into the Lightning port of an Apple device. You would have to transfer the pictures from your iPhone 8+ to your computer first, then back them up onto this flash drive from your computer. If you are looking for the convenience of something that can plug directly into your iPhone, look for the SanDisk iExpand. Best Buy does sell them. They come in a few different memory sizes. They have a lightning plug on one end and a USB on the other. You can plug it directly into your iPhone and use their app to back up the photos to it.