Need to find 4500 images, is there a way to do a bulk search and download all the images at once?

No, this feature doesn't exist. Be aware that a search term will often pull up extra files that you aren't looking for. A search for "ABC" will bring up "ABC.foo" but also "ABCDEF.foo".

Be sure to sync then disconnect from Box while using Bridge, as Bridge is NOT cloud-aware and you can have conflicts.

I would look for a bulk file search utility that works directly on your drive and skip Bridge for this.