How do I update Safari on my iPad

You can’t, by itself.

Apple iOS/iPadOS Safari gets updated with iOS/iPadOS upgrades/updates.

Here are my questions to you.

What year and model iPad do you have/own?

The “A” model number can be found on the aluminium back of your iPad, in small print, right under the larger bold print “iPad”.

What iOS/iPadOS version is this iPad, currently, running?

You cannot update it separately unless such an option presents itself automatically because Safari is installed as part of the iOS. So you would need to upgrade the iOS if your device is compatible.