How to Use Find People at Companies Without Duplicate Charges for Existing Salesforce Data?

Hello! Good morning from PST 🌞 I have a question for you. I have a list of companies my Sales team is interested in pursuing. I crossed this list with the contacts in our Salesforce and have 84 companies with 700+ contacts. My next course of action is to fill in the missing people (and add emails) for the C-suite. I was watching some of the trainings and it seems like I can use the Find People at Companies function, but how do I ingest the data I already have so I am not charged for it? This is basically a gap analysis. Thanks for your time!