Recovery through brute force is only possible if the search space is small enough that can be checked within reasonable time.

So the first step is to shrink that search space as much as possible. So for example you have to first figure out how many words you actually have. Why is it a big range (30 to 50) instead of a fixed value?! Just count them already...

Then start checking them against a word list trying to eliminate invalid ones to reduce that search space.
But to do that, you first need to figure out how you created the mnemonic in first place. Although there is a popular and most used word-list standardized by BIP-39[1] but other wallets like Electrum, blockchain.info, etc. have used different word lists and algorithms in the past.

Knowing the wallet/tool used is also necessary to know the mnemonic algorithm when recovering your keys. After all you have to derive the child key to check if it is valid.
It would also help if you knew the version of that wallet/tool that you used. For example Electrum has changed its algorithm 2 times if I'm not mistaken. Knowing the year or version of it would help narrow down the algorithm.

[1] https://github.com/bitcoin/bips/blob/master/bip-0039/bip-0039-wordlists.md

P.S. of course if you have "bought" this from some random user on the internet telling you it holds a treasure, you most probably threw your money away and are also wasting other people's time who would try to help you.