SETTING A UNIQUE NUMBER FOR ENTRIES INTO THE ORACLE TABLE USING PL/SQL

I need a simple piece of pl/sql that will create a unique number for each user that is created on my system.  They create an account from a web form that submits to an oracle package.  I want to use this unique number as the primary key so that I can pull an individual's row back from the table.  If you would like to see my code for the package so far, check below:  (thanks in advance!)



CREATE OR REPLACE PACKAGE BODY mintslogin
 IS
     PROCEDURE main (iemail IN VARCHAR2, ipword IN VARCHAR2, same_email IN VARCHAR2, Name IN VARCHAR2,
     phone_number IN VARCHAR2, address IN VARCHAR2, city IN VARCHAR2, us_states IN VARCHAR2, zip IN VARCHAR2)
     IS
     BEGIN
        INSERT INTO demo_table
                    (email, pword, ip, c_name, time_
                    )
             VALUES (iemail, ipword, ip_address, computername, itime
                    );
        COMMIT;
       OWA_UTIL.redirect_url ('http://127.0.0.1/mintsii/payment.html');
               
     END main;
 
    PROCEDURE payment (paypal IN VARCHAR2, check1 IN VARCHAR2, donate IN VARCHAR2, no_payment IN VARCHAR2)
IS
   BEGIN
      INSERT INTO demo_table
                  (paypal_, check1_, donate_, nopayment
                  )
           VALUES (paypal, check1, donate, no_payment
                  );
      COMMIT;


END payment;

PROCEDURE testproc (testval VARCHAR2)
IS
   BEGIN
   OWA_UTIL.redirect_url ('http://www.google.com');

END testproc;

END mintslogin;
/