there is currently no obvious way to do this. You have a couple of choices: 1. Obtain a quote for the detailed migration you are after or 2. if you are good with excel (and most of your transactions go through a bank account and/or credit card) you can extract general ledger activity and with some manipulation and transaction rules you can upload with the manual bank csv data option. The only drawback is that you will need to reconcile the bank statements once you import but most of the work is already done.
Reckon is currently working on an import tool.
Reckon will convert the following for data from Xero for freee - chart of accounts, item list (inventory quantities on hand are not included), customer list, supplier list and employees (name and address only).
Here is the link if you'd like to obtain a custom quote for detailed transaction import.