This guide will let you know how to remap any button in Call of Duty Modern Warfare and Warzone.
First, you will need to press the Playstation button from your controller, scroll up to the top and go to the settings option on the right side of the screen, as shown in the image below.
You have to go to accessibility in settings, then scroll down and select the Button Assignments option.
Enable the custom button assignments and go to the custom button assignment option. You will see all of your buttons remaps there like your controller square button is remap with R3 button through which you can easily pick items.
You can also customize these buttons according to your gameplay. If you want to reset all of these buttons to default, you have to press the reset button on the right side of the screen.