How to update composer 1.6.3 to latest version 2.0.4?

I have tried to update my existing composer version in ubuntu.

and I try to check the version but ubuntu say package not found.

Then I again try sudo apt install composer to install composer.

Now when I checked the composer's version. It shows 1.6.3 and if I try /home/alok/composer.phar then the composer's version is 2.0.4.

I am confused. What should I do?

Please help me to solve this.

Remove the old composer (the one in the repros):

sudo apt remove composer

There will remain a directory with preferences in your home folder. Move that out of the way:

mv ~/.composer ~/was-composer

Then, execute the four commands at the top of this page: https://getcomposer.org/download/

You now have a local version that you can run with php composer.phar. To make it global, first make it executable, then copy it to a directory that lies on your $PATH:

chmod +x composer.phar
sudo mv composer.phar /usr/local/bin/composer

Now you can do composer require... etc., from any directory.

In your terminal type:

composer self-update

or

composer selfupdate

It will be updated to the latest version.