To create a contact and an opportunity from a lead that is associated with a campaign, and keep the campaign member history, the administrator should convert the lead from the campaign member detail page. This will automatically create a contact, an account, and an opportunity that are linked to the campaign. Deleting, cloning, or adding a contact will not preserve the campaign member history. Reference: https://help.salesforce.com/s/articleView?id=sf.campaigns_leads.htm&type=5