How to upgrade Magento 2.x to Magento 2.4?

 Let's Play.

First take to older version website backup and after your run below commands.

Magento Open Source:

> composer require magento/product-community-edition=2.4.0 --no-update

Magento Commerce:

> composer require magento/product-enterprise-edition=2.4.0 --no-update

And You want to more-information check this link - 

https://devdocs.magento.com/guides/v2.4/comp-mgr/cli/cli-upgrade.html

And you want to how to run commands.i have added answer in stackexchange can you Please check :- 

https://magento.stackexchange.com/questions/319193/upgrade-magento-2-3-3-to-2-4/319194#319194

Any query let me know .

THANKS.