Help with restoring database from old version of PostgreSQL

I'm seeking help in restoring a database that was created with PostgreSQL
9.6. I backed it up successfully and have restored it before, but that was
when PostgreSQL 9.6 was still supported. After going through the
installation of PostgreSQL 16.3, I opened up pgAdmin 4 to try to verify the
PostgreSQL/PostGIS installation, but when I try to connect to the
PostgreSQL 16.3 server, I get an internal server error message:
'ServerManager'
object has no attribute 'user_info'.

In pgAdmin4, I am able to connect to the PostgreSQL 9.6 server, but when I
try to verify the install by querying: CREATE EXTENSION postgis;
SELECT postgis_version();
I get the following error message: ERROR: could not open extension control
file "C:/Program Files/PostgreSQL/9.6/share/extension/postgis.control": No
such file or directory SQL state: 58P01

How can I restore my database to have access to it again?

Thanks.