Transactions on the old blockchain won't confirm on the new one. Three possible situations:
1. If you sent coins from a new-blockchain address to an old-chain one, the transaction should re-confirm once you update (because it's on the new chain).
2. If you sent coins from an old-blockchain address to an old-chain one, the transaction is dead - it's on the old chain.
3. If you sent coins from an old-blockchain address to a new-chain one, the transaction never happened - it's on the old chain. The coins should still be in the sending address once it's updated to the new chain and synched.