Need to set my list of 12K so they are CSV ready FOR BULK EMAIL

I require assistance organizing my mailing list of 12,000 contacts into a uniform CSV file format for use in my marketing automation platform. Currently, the email addresses exist individually without standard formatting or file structure. The selected freelancer will need to consolidate all 12,000 contacts, format each row consistently with headers, and save the final document as a CSV file. Attention to detail is critical to ensure a smooth import into my marketing platform. Experience working with large lists and familiarity with CSV formatting is preferable. Quick turnaround time is important as I am ready to launch my next campaign.