Need my username and pasword for router with an IP address of 192.168.1.1

I do not know the username and password for my router that has an ip address of 192.168.1.1.  I am affriad to do a reset on it as I do not know if that will mess up everything that I have on the network.  Also even if I do do that I do not know if I will be able to get on still as I am unsure of the default username and password for this router.

Any help would be appreciated.