How to change windows authentication mode to sql server authentication mode.

If you want to connect to a server using SQL Authentication mode, just select it in your new connection dialog box instead of "Integrated Authentication".

If you want to set a server to accept SQL Authentication and it currently doesn't, you'll have to connect to the server using Windows Authentication (and a user that has the Server Admin role), and in the properties of the sql instance, you can change the authentication mode allowed.

I think you havent understood the question.
I want to reset my mode to sql server authentication mode.
and set password for sa
i have changed the security to Windows and Sql Server authentication mode.
How how to set the passwod of sa
alter user sa enable
alter user sa enable with password='admin12'
Is it ok

The two options are "Windows Auth" and "Windows or SQL Auth" - there's no option that allows just SQL logins, so you'll have to leave it on the current "Allow both" option if you want SA to work.

Otherwise, yes - just enable the SA account and reset the password (which is likely blank) and you should be good to go. Especially since the account was previously disabled, there are no side-effects to doing that.

I think you have not understood the question, the taskyou are telling is very simple and any1 can do that.
I am asking for commands.
to active sql server authentication.

ok