I want to know the model of the modem by using model number - C050900P031A
That part number is a discontinued ePMP 1000 5 GHz Integrated Radio (FCC). Your replacement options are the ePMP Force series (180, 190, 200) or ePMP1000 connectorized.
https://www.cambiumnetworks.com/products/pmp-distribution/#epmp-products
