Wireless Bridge - lost the access to the bridge router

I sucessfuly set up my R6700 AC1750 to wiress bridge (wifi -> Lan) and connected it to my desktop via Lan port on router

My desktop is connected to internet via wireless bridge and my main router (other brand)

I have no access to the main router, and I prefer not to reset my bridge router if possible :)

How do I access my netgear router? On my desktop I used "ipconfig" command, then the only IP address I got was my main router (192.168.31.1), I 've lost my bridge router's IP address. 

Thanks in advance!