Hi,
Is the abc field is a form field which has been mapped to a custom field in Contact entity?
If yes, you can follow the next steps to achieve it.
1. Since the field in Contact entity will be updated with the submission of the marketing form, the trigger of the flow can be set as the following:
2. Get the created / updated contacts.
3. List all of the accounts.
4. Compare the Account Name with the abc value one by one.
5. If they match, update the Account name lookup field in the Contact record. Otherwise, nothing will be done.
