Can the iOS 13.6.1 be updated on my ipad

Go to settings— General— Software upate. If it says that 13.6.1 and IOS is upto date means its the latest version for you ipad and it cant be updated past 13.6.1. You need to get a new ipad to get the latest IOS.

No. Any device which is running on iOS 13.6.1 can run iPadOS 15.4.1.

To the OP. You have simply skipped a lot of updates at this point. Use your home computer to update iPadOS to the current version.

See this link for help --> Update your iPhone, iPad, or iPod touch - Apple Support

Contained in the link is the following:

If you can't see the update on your device, use your computer to update your device manually. Learn how to update your device manually if you're using a Mac with macOS Catalina or later, or if you're using a Mac with macOS Mojave or earlier or a Windows PC.

Click the blue words and follow the directions to use your computer to update.

Not sure why Apple recommended your post. It is actually not correct.