I would attempt to brute force the wallet, or if you had an idea of what the password might be, try iterations if it. I would split 50/50 if successful.
You have any other proof, evidence, emailed receipts of purchase, documentation, something to prove it's legit?
OP is probably just trying to get a quick buck. Seeing as how they have been online recently but has restrained from posting any more and that they are choosing Telegram as a medium for communication, I would suspect that there is no .dat file.
And even if there is, like Forts pointed out, there's a contradiction between OP's statement (bought coins) vs. the fact that they were mined.
They probably just looked for some old and inactive rich wallets to try and pull a fast one. Don't waste your time. /thread