Pat wrote:

3 of the cameras must use 2.4 GHz wifi. My personal wifi easily
covers my unit and surrounding area, but barely covers the common area
where those 3 cameras are located. That area is roughly 180 feet from
my router, so the limited coverage is not a surprise. Quite a few
years ago, I purchased a TP-Link WA7210N access point. It is
connected to my router via ethernet and is aimed toward those 3
cameras.

An extender? An extender extends WiFi range. You can put more than one
in series.