Back in 2016, I had a Bitcoin wallet with a couple of euros worth of Bitcoin. I used the Android app "bitcoin wallet" to backup my wallet but I had to use a password.

This week, I found the wallet save file but I had forgotten the password. Now I want to try to decrypt it, but the file doesn't have a .dat extension, it doesn't have an extension at all.

What format does Bitcoin wallet use? And how can I try to decrypt the wallet?

I do probably know part of the password, it's just that I don't remember what numbers I put after the password.