Since you still have your Byron era wallet and secret phrase i suggest you get yoroi either on the mobile phone or as browser extension in for example chrome.
Then hit restore, select Byron wallet and restore it, once you have checked that everything is in order i suggest you create a new Shelley era wallet again using Yoroi and once that is done (secret passphrase written down and hidden from anyone but you) then you transfer the funds from one wallet to the other (i’d start with a very small amount just to check everything works before sending such a big amount of ada to a newly created wallet).
You could try to restore with the 12 word seed phrase on adalite.io. They do have limited support for Byron wallets.
Or, as @retirementplan suggested, use Yoroi, create a new Shelley wallet there and then go to “Claim/Transfer” (third icon from top on the left-hand side), select “Byron-era wallet”, “Legacy Daedalus Wallet”, “12-word Daedalus wallet”, and try that.
But if Infinito did something different than the standard back then, both might not work. And since they seem to have gone completely out of business, it might be difficult to find out what they did.
Last possibility that I would see, is using cardano-cli on the command line. It can convert private keys to its own format and then create, sign, and submit transactions, but it’s pretty involved.
Thanx, do have noticed that they seem to differ quite a bit yes.
Given the possible trouble due to that discontinued wallet app, your suggestion to use adalite.io first seems wise for @MJ1031 , a quick check to see that the Byron era wallet is accessible using pass phrase.
You could really try the option in the Yoroi Chrome extension. It does offer to claim/transfer from a 12 word Daedalus seed phrase. Don’t know if the mobile version has that option hidden somewhere, but I do know it’s available in the browser extension.
As said, no guarantee that Infinito used the same method as Daedalus, but worth a try.
you should get the address for that private key. If that works, check the address on cardanoscan.io if it contains your funds.
If that has worked until here, it is a huge step further. But we would still need that you make yourself a new wallet, we build a transaction to transfer from that Byron address to the new wallet, and submit that transaction. And for that cardano-cli would need a running and synchronised cardano-node which takes a lot of disk space and a lot of time to synchronise.
So, better first check if we even get the correct keys and addresses to see if it is worth the effort.
Did you manage to do it? I did some experiments a couple of months ago and I managed to do some transactions with Byron addresses restored from 12 words recovery seeds. I can help you restore your address and keys, if you still need help.
You need cardano-cli and cardano-address for this script.
You will need to replace my 12 words recovery phrase with your actual 12 words.
The address will be written in the byron-addr.addr file, and the signing key for the address will be written in the byron-addr.skey file. Keep all the files safe.
Run the script with your words and then search for the generated address on https://cardanoscan.io/. Hopefully you will find your ADA at that address (or at least some transactions). If you did some transactions with this wallet, most likely the wallet generated new addresses for the change, so every new transaction would send the remaining ADA to a new address. But you should be able to change the derivation path in the script and run it again, until you find the address with your ADA.
If you find the address and you need help with the cli transaction, let me know.