Match imported file library to an older collection

Hi,

I have a small problem. Some time ago i purchased a new computer and moved all the files to the new computer. However, the develop settings on my photos was not imported with the files and all the settings were removed.

Since i have a collection file (Lightroom Catalog-v12.lrcat) i did not try to import it correctly the right way and i continued to import new photos and changed settings on a bunch of new photos.
Forward a couple of weeks. The old computer is formatted and my daughter is using it. And now i cannot find a way to merge the older catalog file with all the settings on my new file system.

Is there a way to merge the developed settings from an older catalogue and match the settings to photos with the same name as it had on my old computer in my new catalogue or do i have to browse through all my photos and edit them again?