Old Library won't import

[putaimme]

Hello,

I backed up my old calibre library because my computer had issues I got a new computer and started adding new books as I didn't have my backup (left overseas). I have my backup now but have not been able to get the books into the library. There are over 1200! I've tried the switching between two libraries but it only shows/syncs some of the books not all.
I've tried adding a new user on my computer to start a new calibre library but since I backed up the library, I didn't actually export it it won't recognize it as an exported library.

Any idea on how to get these books in the library without having to do it one by one? St this point I'm tempted to just take it to geek squad.

I'm using Microsoft 7 on a Microsoft Surface.