IP Address for Modem and for Router

I recently moved to using a separate modem and router (in the garage).

When I set up the Modem it was 192.168.1.1. Then I ran a piece of software which set the modem in bridge mode.

I set up the Router, again with 192.168.1.1 and both are working OK.

Later it dawned on me that I couldn't access the Modem using 192.168.1.1.

If I can give the modem a separate IP address from the Router then would I be able to access the Modem?

If so, how should I do this:

Router: 192.168.1.1 (and IP addresses to start at 192.168.1.3)?

Modem: 192.168.1.2?

or should it be vice-versa

or something else.