Prepend a number to all files names in a directory

ls | Rename-Item -NewName {"1" + $_.name}

• ls lists all files names in the current directory
• | forwards the names to the Rename-Item command
• -NewName renames the item to the name shown in the brackets
• $_.name refers to the old name forwarded
• „1“ + $_.name prepends 1 to the old name