The LIC-MX68-ENT-1YR would provide a basic level of functionality for 1 year, whether you need that or advanced security, only you/your customer can say. You should be able to select longer terms as well.
I suggest you take a look at this article for descriptions of what is and isn't available in GovCloud:https://documentation.meraki.com/Platform_Management/Cisco_Meraki_for_Government/Cisco_Meraki_for_Go...
Regardless I would be talking to your Meraki Rep. Government requirements are complicated and different between Federal, state, etc and the government reps and SEs are trained for helping with these items.
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