How exactly did you check the wallet.dat file balance?

If you check the wallet.dat file through the newly installed Bitcoin core there is a possibility that the wallet is showing a balance while the core is syncing and not fully synced yet?
If you can post the BTC address of that wallet.dat file we can check it on Block explorer to make sure you are not bluffing.

There are lots of newbies here telling that they found a wallet.dat with a large amount of BTC but most of them are bluff and they mostly created a thread for hunting merits.

Why not use the recovery service which is already posted by OmegaStarScream?