On your Mac, select the items, then Control-click (or right-click) any one of them. In the shortcut menu, choose "Rename Items". In the pop-up menu below "Rename Finder Items", choose to replace text in the names, add text to the names, or change the name format.
"Replace Text": Enter the text you want to remove in the "Find" field, then enter the text you want to add in the “Replace with” field. "Add Text": Enter the text you want to add in the field, then choose to add the text before or after the current name. "Format": Choose a name format for the files, then choose to put the index, counter, or date before or after the name. Enter a name in the "Custom Format" field, then enter the number you want to start with. Finally, click "Rename".