Information Lost between lead and becoming a potential/client

After I upload a lead, our sales rep goes in and sends emails and puts in notes for the lead. Once they designate that lead as a "potential" and an account is created, we lose the "notes" and "emails sent" information that the rep had put in.

I've tried the mapping, but cannot seem to find where to make sure all of the lead information gets transferred to their potential and account information entirely.