How to find your “administrator’s password “?

You cannot find, as it is encrypted. You can only reset to a new password

https://support.apple.com/guide/mac-help/reset-your-mac-login-password-mh35902/mac

If you use FileVault, you may need your FileVault key. If you escrowed your FileVault key with Apple using your Apple ID, you may be able to get your FileVault key that way. Again, assuming you used FileVault to encrypt your disk.

In Sys Prefs>Users & Group, does it say admin under your name?

administrator or admin means that person or account has the rights to change things.