This error happens when there is some sort of output on the page before the header function is used to redirect to another page.
This part of the error:
output started at C:\Inetpub\www\WACART1\confirm.php:142
is saying the output is at line 141 or 142.
It may be a blank space after a closing php tag:
or a blank line after a closing php tag before the next opening tag:
See the following for more details: