This wikiHow teaches you how to change the names of multiple files at once in macOS.
Steps
1Open Finder 
on your Mac. You’ll usually find this icon on the Dock.
2Open the folder with the files you want to change.
3Select the files. To select more than one file at a time, hold ⌘ Command as you click each file. If you prefer, you can click and drag a box around the files you want to edit.To select all of the files in a folder, click somewhere in the folder, then press ⌘ Command+A.
4Click the Action button. It’s at the top of the Finder window.
5Click Rename Items.
6Click Format from the drop-down menu. It’s the menu at the top of the set of rename tools.
7Select a name format for the style format. Select Name and Index, Name and Counter, or Name and Date depending on your needs.
8Type a name for the files into the “Custom Format” box. This is the name that will appear at the beginning of each file name.For example, if you type “Cat” and selected “Name and Counter” as your format, the files will be called Cat-1, Cat-2, etc.
9Enter a starting number. If you’re numbering the files, you can start with 1, 2, or any other number.
10Click Rename. The selected files are now renamed sequentially using the formatting you entered.
