If we're talking about USB-connected external drives, like the Western Digital (WD) drives of my post and the OP, you can start by just copying the contents of your current drive to a new USB-connected drive. I bought mine together, at 4TB capacity each, and selected a 'red' box and 'blue' box for simplicity. If you follow the oft-repeated Lightroom "best practice" of maintaining your image files in YYYYMMDD named folders (example: 20240124-Disney Exhibit), you can easily find and copy ongoing changes to the primary drive to the secondary copy after that initial mass-copy of data. This mass-copy is performed outside of Lightroom, just using your computer's OS. Giving better, more details instructions is a matter of having a specific issue and / or actual equipment to describe. You also need to copy (back-up) the folder with your LRCAT.

Drive failures a very scary event. Many years ago I ran my studio on MacG3. Everything was on the one internal HD. It crashed and I was scared, ALL my records were on it. I found a business that recovers data, and for only $2600 they recovered 95% of the data. They suggested I use an external backup drive, so I bought two 4tb drives so that when one should die, and they can and will fail after a time, I can just trash the failed one, buy a new one and copy the data from the remaining drive and be right back in business. I now utilize three sets of drives like that and have not had any more problems. In the future I plan to replace that setup with SSD's and perhaps not worry about the mechanical HDs.