Importing Accounts and Contacts from Seperate CRM files.

Importing Accounts and Contacts from Seperate CRM files.

We are new to Zoho. We used to use SFDC. And we retained our data from SFDC. However, the way SFDC manages contacts and accounts is to relate both to an Account ID. While trying to upload our separate Account and Contact CSV files, we were unable to map the contacts to the accounts using the unique Account ID? We were told by Zoho CRM support we would have to create a 3rd spreadsheet that captures the Account Name and the Contact Name in the same row. Great. But there are about 3900 Accounts and almost the same number of Contacts. And I really don't want to have to manually create a 3rd spreadsheet. Any thoughts?