Have I lost my Photos due to external HDD transfer problems??

I was recently backing up my photos into my external harddrive (initiated by dragging the mac "photos" folder into the external HDD folder), and the cord accidentally disconnected during transfer. I just wanted to confirm that all of my data is still with my computer. I do not recall the original size of the folder unfortunately, as that would have been the best way to determine whether it got lost or not. I know if you are cut pasting something "within" the computer -- any unexpected interruptions would corrupt the file because the file is moving to a new location and is now lost in transition. Does this apply here as well? Because the "photos" folder is not actually moving anywhere -- only being copied -- should I feel confident that all my files are intact?

HDD: Seagate Backup Plus

Thanks!