compile a program in terminal with .jar

[flex567]

I created Myproject folder. Inside I have 3 folders:
/lib
/src
/bin

Inside src there is a .java file:

	public class hello_world{
	     
	     public static void main(String[] args){
	        System.out.println("Hi, from hello_world");
	     
	        seba.st.hello_world_package test1 = new seba.st.hello_world_package();
	 
	        test1.packFunc();
	    }
	 
	}

inside lib is a .jar file which I created from this .java file:

	package seba.st;
	 
	public class hello_world_package{
            
	    public void packFunc(){
	     
	        System.out.println("hi from pack_func!");
	    }	 	
     }

I am trying to run this program from terminal with this command

	javac -d bin -sourcepath src -cp lib/packEx.jar src/hello_world.java

and I get this error:

	src/hello_world.java:11: error: cannot find symbol
	        test1.packFunc();
	             ^
	  symbol:   method packFunc()
	  location: variable test1 of type hello_world_package
	1 error

What am I doing wrong ? How can I compile and run this program from terminal?