data recovery – No boot Device found on centos Linux server in raid 5

We have dell emc r440 server installed os in centos 8 actually today my server suddenly stucked on login screen after entering user name so my colleague forcefully shutdown it after that it is not booting just reflecting no bootable device found …
Detail are
Os:- Centos8
raid configured:- 5
Harddrive:- 3TB (1.2TB each)
Actually I m new at Linux field so please guide me how can I recover it or login to centos os on server please someone guide me or help thankyou in advance ????

I already run some trouble shooting by watching YouTube and Google document but not helpful for me.i need details guidance what to do under this situation and recover data successfully without loosing it.