I used 17 word phrase to restore my password to this account after blockchain was updated to the new wallet.
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You have plenty of options, just get the privatekeys on iancoleman.
it is by no means compatible to BIP39 recovery seed, but the new bc.info wallet does have a BIP39 mnemonic seed
if simply upgraded, old wallet addresses should be there somewhere,
you can try what BitMaxz said and check all your old BTC addresses there
you need to extract one by one those private keys because legacy wallet bc.info is not HD wallet