Macbook Pro late 2012 can't copy files to external hard drive

I purchased a seagate external hard drive a year ago and started moving files to the hard drive and have done so up until now. Nothing has been done to the external hard drive and I have plenty of space as I checked. The only thing that has changed is I updated to MacOS 10.13.1 two days ago. when I plugged my external hard drive I was asked if I wanted to use with time machine and I declined. I opened the external hard drive and the folder icon format is completely different and there are no columns. I see folders but no dates, no subfolders and no preview as well as I can no longer copy files and photos either. Please help. Thank you.