Linux basic files tools

Hello! Instead of asking AI, I wanted to hear from community what are some great Linux CLI tools that you find useful? My specific situation currently is this: I need to backup an old suspicious HDD that contains family pictures to load up on grandparents new sdcard digital photoframe. I basically just want to use cp and df to check the size of contents. But I know that df is tricky with the actual size of items or something. What are some other basic useful tools for potentially unhealthy disk drives?