These steps will guide you to upgrade your personal account to the organization one:
Before you can enrol as an organisation, you need to retrieve your D-U-N-S number of your company. This can be retrieved by contacting Duns & Bradstreet here: https://www.dnb.com/duns-number.html
To convert your account type, you need to submit a request to Apple Developer Program Support.
Click on this link to go to Contact Us form of your Apple Developer Program.
Log in with the Apple ID and Password associated with your existing Apple Developer Program, if necessary.
Fill out the form by selecting your Region and choosing Account Updates and Renewals as your Subject.
In the message field, you can tell Apple that you’d like to update the account to company/organization. Don’t forget to write the CEO name, Company/Organization name, DUNS number, address, and phone number.
Apple will usually call the phone number listed to verify your enrolment within two weeks after the request. After Apple calls and verifies your enrolment, you will receive an email from Apple asking you to fill out additional information about your organization. Please follow the instructions in the email accordingly.