Router or router/modem - for security cameras without use of internet

Hi,

I currently have an modem which i think is also a router,it connects to australian nbn internet.
I am wondering how my security cameras and computer would work with a router/modem for nbn [australia] if i am not connecting to the internet ? I am not connecting to the internet at all,the cameras also do not require the internet.Would i need a router/modem that does not connect to the nbn {australia] and is a router on its own and not a modem as well?The internet is not involved in the connection of the computer and the security cameras.
I am not sure but i think my modem is also a router,it connects to australian nbn internet,and apparently i can access other devices thru it,but have only done that once,so not sure if this is the best sort of router/modem to use.
Also,is there a higher security router available?What sort would they be?

thanks in advance

windows 10

Samuria said:

Any router will do its a matter of setting the tcip on the cameras and pc do you know the ip range for camaras?

hi,yes i can get it,should be there.The cameras are usually connected to the internet though but they are supposed to work without the internet also.
Another question - Will all cameras work without the internet but with a router if they are meant to be connected to the internet [?]I am told that the cameras that need the internet connection go through the camera manufacturers servers. ?

thanks