Async Task Help

How am I supposed to make this work, I'm unsure where to go from here.

Cannot implicitly convert type 'System.Threading.Tasks.Task<Square.Models.ListInvoicesResponse>' to 'Square.Models.ListInvoicesResponse

Cannot implicitly convert type 'System.Threading.Tasks.Task<Square.Models.ListInvoicesResponse>' to 'Square.Models.ListInvoicesResponse