First you must accept the quest Heart of Deimos and complete it. With this you will now have access to Necropolis which is right next to Cambion Drift inside Deimos and you will receive the Xaku warframe blueprints. Once arriving to the Necropolis you will need to talk to Mother and find the corresponding bounties that have the Xaku Neuroptics, Systems, and Chassis blueprints.
There are 3 bounties in total you need to complete and the loot pool for each bounty normally has multiple uncommon and rare blueprints you can recieve. Which means you will not always receive the Xaku blueprint you want. It is pure RNG. You may have to run each bounty multiple times to receive the blueprint you want.