My old iMac died..... 'Photos' Question

My old iMac died and due to it's age, I decided to get a new iMac rather that attempt a repair on the old machine.

This necessitated relocating my massive photo library to a different drive. The old mechanical HDD was 1TB larger than the new SSD drive....

Is there any quick way to get 'Photos' to find the photos in the new location? Or, do I need it completely rebuild it from scratch.