How to get the list of users from a sharepoint group with specfic permissions(permission level) using powershell.

Hi ,

We have a requirement where we need to get the list of users part of "Content Admin"  group in each sub-site. This group has a custom permission level mapped to it ("Content-Edit"). All these subsites has the unique permissions (Broke inheritance). I tried using CSOM and Powershell to generate the report. but I am unable to get the groups from specific web. Couldn't find any option like $web.Groups to get the groups specific to the web and only could see $web.SiteGroups which pulls all the groups in the site collection. 

Can you please guide / help me with achieving the above functionality?

Thanks,

Venugopal