You can change using of PIN to using of password in Windows 11 easily. All you need to do, is to disable the using of PIN and then add a password, if it is not already created.
Go to Settings
and choose Accounts
In Ways to sign in
section, click on PIN (Windows Hello)
to show the options and click on Remove
Confirm the removing of PIN by clicking on Remove
Then click on Password
to add or change password:
Windows 11 is usually linked to some email account. If you use Outlook.com email services, then current Windows password may be the same as your email account password.