If you have not yet exported data fro your previous account, please see Importing and Exporting G Suite/Google Account Data and follow steps for Exporting Data.
- Log in to Google Contacts web application
- Click More followed by Import...
- Click Choose File
- Browse to the Contacts folder within the Google Takeout data folder exported from your previous account. Select the Contacts file you wish to import and click Open.
- Click Import.
- Once the import has completed, click the Find & merge duplicates link.
- If your import created any duplicate entries, you will have the chance to merge contacts.