Could you help me find a php file?

Hi there,

Could you please tell me what is the php file containing the "Please check the appointment details below and confirm" phrase, which is in the confirmation box. I would like to ask this, since I want to add a short paragraph, explaining that my customers should leave their skype name on the notes field.

I've been trying to locate the file, that's containing this phrase, but Icannot do it. Could you please point me out to the right direction?

Thank you very much.