OK. if you still have your old Mac,the first thing to do is to launch iMovie 9 and consolidate media .
This ensures that everything iMovie needs is in your projects and events folders.
If you did not do this before it is likely the reason for your broken links.
No when you copy these 2 folders to your new Mac (in place of the ones you have on it now) they will not have any links back to your old machine and they should update to iMovie 10 OK.
In the old imac :
The projects are already established . Some songs I relocate , imovie says it can not find it to consolidate , but I can not hear in the project.
That's not the biggest problem because they are a few songs which changes location and can put them back in the projects.
In the new imac :
I copied the folders " iMovie Projects " and " iMovie Events " from my old iMac to my new mac.
I updated as described in this link:
songs not found on the old imac still find them, but in itunes it indicated the correct location.
( That's not the biggest problem because they are a few songs and I can put them back in the projects. )
But of all the audio sound effects themselves are bound in old imac does not find the new imac .
I should copy the folder where I have my old imac sound effects and copy on my new imac, and can even be found in 10.0.2 imovie