I see the new update but there is no option to update

As above: Connect to a WiFi network.

Connect it to the charge circuit, and leave it connected during the update process.

Also, turn off the Automatic update option, and manually check for the update.

What happens when you attempt to update?

Any error messages?

What is the existing version of iOS?

It can be updated to iOS 15.7.2.

Connect to a WiFi network.

Charge the battery and preferably leave it connected to the charge circuit.

Check for the update again.

You are quite welcome.