I would like to know Cmdlet to get list of allowed and blocked file extensions on hub and edge . Please sugge

Attachment filtering is only available on the Edge:

https://technet.microsoft.com/en-us/library/aa997139(v=exchg.150).aspx

Manage attachment filtering on Edge Transport servers

If you have hub transport rules that use attachment inspection, you can set or view those on the Hub or Edge role.

https://technet.microsoft.com/en-us/library/jj674307(v=exchg.150).aspx