Box2D meters and pixels

I am confused about pixels and meters in Box2D. I know that Box2D work only in mters so I need SCALING FACTOR. How big I need it? For example I want that from my mouse coordinates position X and Y for example(1527, 30) throw an Box2D object how I need to do that?
if my scaling factor is private final static float PPM = 1/100f; so my

x = 152,7,
y = 3meters

Here is my code

private void setBox2DFigures(){
        world = new World(new Vector2(0,-9.81f), true);
        rend = new Box2DDebugRenderer();
        cam = new OrthographicCamera(); // Camera 
        body = new BodyDef();
        bodyPhysics = new FixtureDef();

        CircleShape c = new CircleShape();
        body.type = BodyType.DynamicBody;
        c = new CircleShape();
        c.setRadius(20*PPM);
        c.setPosition(new Vector2(Gdx.input.getX()*PPM, Gdx.input.getY()*PPM));
        bodyPhysics.shape = c;
        world.createBody(body).createFixture(bodyPhysics);
}

and here in a draw method I want to coin position set to my mouse position

public void draw(){
    c.setPosition(new Vector2(Gdx.input.getX()*PPM, Gdx.input.getY()*PPM)); // mouse coordinates * PPM
    rend.render(world, cam.combined);

}

But I don’t see anything in my screen. Whats wrong? How I need to choose My scaling factor(PPM)?

here’s my main

public class DesktopLauncher {
    public static void main (String[] arg) {
        LwjglApplicationConfiguration cfg = new LwjglApplicationConfiguration();

        cfg.title = "Catch Me!";
        cfg.width = 1800; //1800
        cfg.height = 900; //900

        new LwjglApplication(new Game(), cfg);
    }
}