Step: 1 => Open your Shopify admin panel.
Step: 2 => Click on the Settings button from the side menu and choose General (See the screenshot below).
Step: 3 => Now click on the Change Formatting link inside the Store currency section (See the screenshot below).
Step: 4 => Copy the following code.
HTML With Currency
<span class=money>${{amount}} USD</span>
HTML Without Currency
<span class=money>${{amount}}</span>
Step: 6 => Now click on Save Settings button.