Changing accounting software is less about moving data and more about proving that nothing changed in the move. An import that completes without errors is not the same as books that match.
Prepare first. Agree the cut-over date, close the period cleanly and decide how much history you need to bring across. Map ledgers and groups deliberately rather than accepting whatever an import guesses.
Then reconcile. Compare the trial balance, ledger balances, outstanding receivables and payables, and opening balances between the old system and the new. Check voucher counts for the periods you moved.
Keep a written record of what moved, what matched and what needed correcting, and ask your accountant to review it. Running both systems side by side for a short period can add confidence before you rely on the new one.