How was can i use iPad to unlock iPhone

No, it is not possible.

See the following Apple articles:

If you forgot your iPhone passcode

If you forgot your iPhone passcode - Apple Support

How to remove your iPhone, iPad, or iPod touch passcode without a computer

How to remove your iPhone, iPad, or iPod touch passcode without a computer - Apple Support

How to remove Activation Lock

How to remove Activation Lock – Apple Support (UK)

• If you need help removing Activation Lock and have proof of purchase documentation, you can start an Activation Lock support request.

You can also contact Apple support for help, -> Get Support (apple.com)

You have to show proof of ownership of your product, provide all documentation showing your purchase of the device.

If you do not have additional proof of ownership, contact the reseller. They may be able to provide the original purchase document.

Once Apple receive your proof of ownership, Apple will further review your request and provide an update.

Not sure why you want to use via your iPad (?), If you don't have a computer:

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