I know that we can use next code on device side:
licenseInformation.ProductLicenses["product"].IsActive
But I want to check purchase on my server. How can I do it?
If I understood you well, the new Windows Store APIs will be good for you: https://msdn.microsoft.com/en-us/library/windows/apps/mt609002.aspx
If you have a catalog of apps and in-app products (IAPs), you can use the Windows Store collection API and Windows Store purchase API to access ownership information for these products from your services.