Photo Library transfer to external hard drive
I transferred my Photos to an external hard drive some 2 years ago - successfully. Today I tried to transfer again, having deleted the original Photos Library on the external hard drive first. All goes well until about half an hour into transfer, it says the following: The operation can’t be completed because an item with the name “Photos Library” already exists. Howerver, when I check the external hard drive it certainly doesn't exist anywhere...! What has gone wrong? Much appreciate any help.
iMac 27″, macOS 10.15