External Hard Drive video library

I have a large collection of videos on my laptop that I'd like to upload to an external hard and connect this to my Mi Box (Android 8). But the HD has to be first formatted by the Mi Box which makes it unrecognisable by my laptop - so then it becomes impossible to load any videos on to it.

Anyone know a way around this? Is it possible to connect and format a HD to the Mi Box and then upload videos to the mi Box?