Switch backup drive to replace original crashed drive in LR
My external drive (drive A) containing photo files crashed and cannot be recovered. That drive was backed up by another drive (drive B). All LR catalogs are on computer with drive C. Catalogs are fine, I know where they are, and they are also backed up on drive B. What is the process to inform LR that drive A is dead but its replacement should be drive B? The folder structure is similar to that of drive A (or can be made to mirror drive A). There are 50K+ photos referenced by the catalog. The folder structure is by year and date.