calibre import problem

I have a brand new iMac running Sierra, and want to migrate my calibre library to it from my old Macbook Pro. I exported the library from the Macbook (calibre created a file named part0001.calibre-data) and put it on my new iMac. I then downloaded and installed the latest Mac version of calibre. I moved the exported file to a new folder, then pointed calibre to it from the Import menu. I get an error message saying that the folder is not empty. When I empty the folder, it says there is no data. Please help.

Thanks! :)