HI ,
I think you are looking for MS Defender for Endpoints. There are different plans for Defender Endpoints that you may need to consider for your deployment based on the features that they offer. Check below URL
As far as onboarding is concerned , there are different options that you can utilize based on the workload ,whether if is server or Windows client. The below will give complete overview of the onboarding process
However , if your servers are in Azure and you are using MS Defender for Cloud(previously Security Center) , there is a unified solution for onboarding that you can use to seamlessly onboard servers from Defender for Cloud to Defender for Endpoints