I used to use a fantastic applications called "The Rename" that was fairly intuitive and fairly well designed. But it looks like it's no longer developed and isn't supported under Windows 10, and can only be found on sites like Softpedia which I rarely trust.

I've used this other program called Bulk Rename Utility. It has a ton of options but it's hard to figure out. Whenever I do a bulk rename, I ALWAYS do it to a copied folder of the files I'm working on. Never the original.