Convert 'System.Object[]' to type 'Microsoft.Dynamics.Ax.Xpp.XppObjectBase' in X++
Casting is impossible - these types aren't compatible.
But a conversion is possible. For example, if you have System.Object[] containing strings, you can iterate them and put them to List class in F&O. The exact solution depends on what you're doing, which you didn't tell us.
Also, XppObjectBase is an abstract class that you can't use as such, but it's a parent of all native X++ classes. You'll need to use a a non-abstract class instead of XppObjectBase.