I don't know my administrator name

Hi similevi77,

It seems that you improperly changed your account name. Doing so usually results in a loss of administrator privileges. Please read the below procedure for resolving this issue.

If no administrator accounts exist on your Mac, an exploit exists in macOS that permits you to re-run Setup Assistant and create a new administrator account. This administrator account can be used to resolve the issue and restore administrator privileges to your real account. To perform this exploit:

1. Verify that you are not in one of the scenarios listed below:
   1. A firmware password is set on your Mac. You'll need to disable (turn off) the firmware password first.
   2. FileVault is ON, you don't know the password to any FileVault-authorized user accounts, and one of the following scenarios apply:
      1. You set an Apple ID to unlock your startup disk. Follow these instructions to reset the user account password for the user that set up FileVault.
      2. You set a local recovery key, and don't have the recovery key.
2. Boot your Mac into Single User Mode by holding down Command-S as you turn on or restart your Mac. Release the keys when white text appears on a black screen.

   If FileVault is on, the login window should immediately appear. Log in as any user to continue.

   1. If you only have the recovery key, select any user and enter the password incorrectly three times. Then, choose to use the recovery key. Enter it exactly as recorded, including capitalization.
3. When the white text stops moving, enter these commands in order, very carefully:
   1. mount -uw /
   2. rm /var/db/.AppleSetupDone
   3. reboot
4. Your Mac should restart immediately after the reboot command. (If FileVault is on, log in to continue or use the recovery key.) Setup Assistant should soon appear.
5. Progress through the Assistant until you're prompted to transfer data. Choose not to; this will permit you to create a new administrator account on the next screen. Use a generic or random name to help distinguish this temporary account from your real account.
6. When Setup Assistant is complete, you'll be logged into the new (temporary) administrator account.
7. Reverse the name change on your real account that you made earlier, then follow the steps in this article to correctly change your account name: Change the name of your macOS user account and home folder - Apple Support

To restore administrator privileges to your real account:

1. Log out of your real account, and log into an administrator account.
2. Open Users and Groups preferences, then click the padlock and authenticate with administrator credentials.
3. Select your real user account and check the box next to "Allow user to administer this computer".
4. Restart your Mac.
5. Log into your real account, and go to Users and Groups preferences. Click on the padlock and authenticate with your own credentials.
6. If desired, delete the temporary administrator account.

Hope this helps!

Go to /DiskDrive/Users/ where you will find your Home directory. The name of that directory is your Admin name.