How do I upgrade MacBook Pro 2012 to latest macOS for HP smart tank 650?

No. The MacBook Pro (13-inch, Mid 2012) can run up to (and including) macOS 10.15.7 (Catalina), but no higher.

That said, you should be able to download a version of the HP Smart Tank 650 driver that is compatible with macOS 10.15 from Hewlett-Packard's website here:

https://support.hp.com/hr-en/drivers/hp-smart-tank-plus-650-wireless-all-in-one-series/18695943

While it is true that the HP Smart for Desktop app

(https://apps.apple.com/us/app/hp-smart-for-desktop/id1474276998?mt=12)

appears to require macOS 11.0 or later, you may want to investigate whether a workaround possibly would allow continued use of macOS 10.15 Catalina with this printer.

First of all, the HP Smart Tank Plus 650 Series is listed as supported in About AirPrint - Apple Support (en-us edition January 13, 2025).

Generally speaking, an AirPrint printer can be used without additional drivers/software when connected to the same network (Wi-Fi router) as a MacBook Pro running macOS 10.15 Catalina.

A printer manufacturer may provide software for setup, ink management and similar purposes. Such software may not be absolutely necessary, but could be a requirement in cases where an ink subscription agreement has been signed.

If a requirement for certain (setup, et cetera) steps, have you checked whether the HP Smart app for iPhone or iPad could be used instead?

https://apps.apple.com/us/app/hp-smart/id469284907

Alternatively, if necessary, an Android version?

https://play.google.com/store/apps/details?id=com.hp.printercontrol&hl=en-US