I have a iPhone 6 and need to update security, even if I pay for it. Can I get updates on my phone for security

Your iPhone 6 is around 7 years old and not compatible with the latest releases of iOS which support iPhone 6S or later. There are no workarounds, Apple only releases security updates as part of the integrated software package. Your only option for the latest security modifications is to upgrade your phone.

Swapping a screen from iPhone 6 onto a 6S is unlikely to provide a satisfactory result.