3 words is relatively easily brute forcible, so you should be able to recover your funds.
The program I would recommend using would be:
https://github.com/3rdIteration/btcrecover/There is documentation on how to use this here:
https://btcrecover.readthedocs.io/en/latest/You will need to first construct a token file with the words you do know.
An alternative approach would be to use this program:
https://bitcointalk.org/index.php?topic=5214021.0Are you certain about the other 9 words? Are you certain they are in the correct order? Are you certain it is the first 3 words you are missing?
Further, do you know an address from this wallet which has sent or received any bitcoin? Preferably the very first address in the wallet, if you know it.
I thought btcrecover only supports Bitcoin Core, now I can see the tool has grown nicely. This is my plan that I will make a dictionary of words I know and put it through the program