I want to change my Quickbooks online company account into QuickBooks online accountant account to utilize maximum features available with Quickbooks online accountants.

QBO Accountant is for an accounting firm. You may open a QBOA account with other email address then invite yourself as the accpuntant to your QB Online data. But should you need to migrate your data, utilize a 3rd party migraion tool to do so.

https://transactionpro.grsm.io/qbo