Need someone to do data export from MYOB Accountright and import into new MYOB file

I have a client using AccountRight 2022.5. In short, they had an AccountRight file up to 2019, then they started a new online AccountRight file from 2020 onwards for some reason. They didn't really know what they were doing and, at some point, someone accidentally imported thousands of random pre-2020 data into the new file, some going back as far as 2014.  It wasn't all the data, however, so the new file is a hodgepotch of some pre 2020 transactions, and all transactions from 1 January 2020 onwards. So the new file is a meaningless mess of all the post 2020 transactions, and some pre 2020 transactions. I have set up a new file to start from 1 January 2020. I have imported the Supplier and Customer cards, Account details etc. I have manually brought in the 31 December 2019 balances and transactions via journals, added the o/s cheques etc. The Chart of Accounts in the two files are the same. I now need to import all the 1 January 2020 onwards transactions from their current file into the file I have created, and then in theory there will be one complete file (December 2019 balances plus all the transactions since then). They will have the file up to December 2019 as a permanent record up to then. MYOB has said they can transfer the existing subscription to this new file, and then the client can continue using the correct file.

My import attempt haven't worked as all transactions seem to just be skipped. I strated with Purchases and Sales as I have read to do, but it didn't work. I don't have the time to work out how to do it properly. Is there someone who has the skills, whom I can engage to do the import properly? There are tens of thousands of transactions.

Please advise. Many thanks

Brad H