Safari is an integral element of iOS/iPadOS - and cannot be updated independently of the OS.
If your iPad has been updated to the most recent version supported by your iPad, then Safari is as up-to-date as is possible.
However, some websites may incorrectly identify your iOS/iPadOS Safari User Agent when used in one or other of its browsing modes - of which their are two - these being Desktop and Mobile. It’s easy to switch between modes if a website isn’t functioning correctly. From the desired web-page, touch the aA icon at the left of the Address Bar; this will reveal a menu. From the menu select Website Settings, then select (or deselect) Request Desktop Website, then tap Done. Now refresh the webpage.
The chosen setting will be sed for the selected website - and can be simply reversed if needed.