Migration of wallet accounts to labels
OK, thanks.
For anyone else doing this type of migration, the procedure I did was :

bitcoin-cli listaccounts   //to get amounts of all balances on each account
copy old wallet to newer version node
bitcoind -upgradewallet //to upgrade wallet to newest version

This procedure preserves all keys, addresses and makes account a label so now when you enter bitcoin-cli listlabels you get all labels as were accounts before

Since label can not have any balance, in separate database enter balance of each account/label from first step.

While upgrading make note of new transactions that should be added to wallet and run

bitcoin-cli listtransactions XXX where XXX is number of last transactions you want to see

add each new incoming transaction (if any) to database balance so balance in database match balance on wallet


That is it. Seems complex but it can be done in no time even for large number of accounts.
Best regards