Stuck importing books back into calibre on new pc

I've just got a new pc . Followed the instructions to export my nearly 3000 book library to an external drive.
Today I followed the instructions to import the books back into calibre.
It starts and I view it naming all my books
But when I get to 100% it says its unable to do it
Chose another empty folder
I have created folders in my docs. Called calibre, calibre books, ebooks etc
But calibre will not import the books into anywhere
Help! I love my calibre but tried all afternoon to import back into it
No luck.:angry::blink::o