I no longer have my administrator password

https://support.apple.com/en-us/HT202860

It is easier to reset the password.

1. Restart in Recovery Partition (this assumes you are using an Intel iMac) by holding down Command + R on startup. If you own a M1 based iMac shut down the Mac, and hold down power button until "Loading startup options" appear and follow the prompts
2. Open Terminal app, hint please look in the menus
3. In Terminal type resetpassword and follow on-screen prompts.