I have looked and can't find a definitive answer to this question.
I have installed a NAS and transferred all my photos from my computer hard drive over to the NAS
Now of course LR cannot find the files. I have a lot of files to transfer (find).
I can only see a method where you select each folder individually.
Is there a way you can do a bulk find?
Say in your original setup you have got a real arrangement on disk of
[localdrive] / folder1 / LRphotos / 2007 / shoot1, shoot2
[localdrive] / folder1 / LRphotos / 2008 / shoot1, shoot2 .... etc
And you have used the OS to move LRphotos complete with all its contents onto the NAS, so it is now at
[NAS] / different1 / different2 / LRphotos / 2007 / shoot1, shoot2 ...etc.
If in your Catalog you can see the common parent folder "LRphotos", then that is what you re-address and the job is done.
If in your Catalog you don't see "LRphotos" but you DO see the year folders, then right-click (Cmd+click) on one of the year folders and choose "Show Parent Folder". Now you DO see that, and can re-address it as above so as to fix the paths of ALL the photos that are nested inside.
If you want, you can then Remove "LRphotos" again, from appearing in the Folders panel - but the key is, having that single point of management available. This is far easier and quicker, than the alternative of re-addressing "2007", then "2008", and so on.