A CSV with a heading row. Columns can be in any order, and only Name is needed:
Name, Type (Service or Product), Code, Category, Description, Price, Cost, Tax, Billed (One time, Monthly, Quarterly, Yearly),
Counted (Per user, Per device), Vendor, Part Number, Track Stock (Yes or No), Reorder At, Order, Location,
Asset Type (Laptop, Switch, Access Point and so on), Make, Model, Warranty (in months), Notes.
Categories, taxes and vendors are matched by name to the ones you have.