Just as you can batch rename photos during ingest, you can batch rename photos in your contact sheet. Select one or more photos and File>Rename Photos... or Command-M or macOS and Ctrl-M on Windows.
You can use variables, code replacements, Hot Codes, plain text, or any combination of these in the textbox. Select the sequence checkmark to add a sequential number to each file (to avoid the same filename).
Select Set {seqn} variable... to specify the beginning value.
To reset the sequence variable to its initial value, hold down the Modifier Key (Option on macOS/Shift on Windows) and select Reset {seqn} variable...
Save frequently used renaming strings as a Snapshot to use at a later time.
