I'm doing a project assignment for school. The assignment is to create a conversion program that 1) prompts the user to enter a value in meters 2) then asks which they want to convert meters to: km, inches, or feet. After the conversion it should repeat the menu until they choose #4 to quit. We have just learned about different methods, so I'm getting stuck on passing the meters value to the other methods. Any assistance is appreciated.

import java.util.*;
 
public class ConversionJMB
{
	public static void main (String[] args)
	{
		Scanner keyboard = new Scanner(System.in);
 
		System.out.print("Enter a distance in meters: " );
		double meters = keyboard.nextDouble();
 
		while (meters <= 0)
		{
			System.out.print("The value must be greater than zero." );
			System.out.print("Enter a distance in meters: " );
			meters = keyboard.nextInt();
		}
 
		menu();
 
	}
 
	public static void menu()
	{
		Scanner keyboard = new Scanner(System.in);
 
		System.out.println("1. Convert to kilometers");
		System.out.println("2. Convert to inches");
		System.out.println("3. Convert to feet");
		System.out.println("4. Quit the program");
 
		int choice = keyboard.nextInt();
 
		switch (choice)
		{
			case 1: 
				showKilometers();
				break;
 
			case 2: 
				showInches();
				break;
 
			case 3:
				showFeet();
				break;
 
			case 4:
				System.out.println("Bye");
				System.exit(0);
				break;
 
			default:
				System.out.println("Choice " + choice + " is not a valid menu option.");	
		}
	}
 
	public static void showKilometers(double meters)
	{
		double kilometers = meters * 0.001;
		System.out.println(meters + " meters is " + kilometers + " kilometers.");
 
	}
 
	public static void showInches(double meters)
	{
		double inches = meters * 39.37;
		System.out.println(meters + " meters is " + inches + " inches.");		
	}
 
	public static void showFeet(double meters)
	{
		double feet = meters * 3.281;
		System.out.println(meters + " meters is " + feet + " feet.");
	}
}