Update without itunes

iPad Pro, iOS 12

See -> Identify your iPad model -> Identify your iPad model - Apple Support

1. 

If your iPad is eligible for an update, then go to: Settings -> General -> Software Update

You can check by reading this Apple article:

iPad models compatible with iPadOS 13 to iOS 15.6.1

iPad models compatible with iPadOS 15.5 – Apple Support (UK)

See the following Apple articles:

Update your iPhone, iPad, or iPod touch

Update your iPhone, iPad, or iPod touch - Apple Support (IN)

If your iPhone, iPad or iPod touch won’t update

If your iPhone, iPad, or iPod touch won't update - Apple Support

2.

Ask a friend, acquaintance or family to use their computer, or at a public library.

Alternately, visit your local Apple Store or Apple Authorized Service Provider and they should be able to help you out.

You will first have to make an appointment due to the pandemic.

Call Apple in your region see: Contact Apple for support and service

Contact Apple for support and service - Apple Support