PL SQL - Declaring Procedure and Function in BLOCK PL SQL

How to add procedure and function in Block PL SQL ,
In This section we are learning how to create a procedure or a function in Initialization ( in DECLARE Section ) in ...
after that , how to call the procedure or the function in logic in body ( after begin) in oracle

declare 
        a number;
        b number;
        c number;
    procedure find_min (x in number, y in number , z out number) is 
    begin 
        if x < y then 
             z:= x;
        else 
            z:= y;
        end if;
    end;
    
    function find_max (x in number , y in number) return number 
    is 
        z number;
    begin 
        if x > y then 
           z:= x;
        else 
           z:= y;
        end if;
        return z;
    end;

begin 
    a := 23;
    b := 45;
    find_min(a , b , c);
    dbms_output.put_line ('Minimum number is '|| c);
    
    c := find_max(a , b);
    dbms_output.put_line ('Maximum number is ' || c);
end;
/

if we're running or execute the procedure block in above, so the output that is ....
-----------------------------------------------
Output : 
Minimum number is 23
Maximum number is 45