You can either opt for Office 2019 which is a one-time purchase or Office 365 which is a subscription-based package. On the other hand, if you are a student then you can simply go for Microsoft Office Home and Student 2016. You can easily have any one of them on your device by just logging in at office.com/setup. But, make sure to go through each product specifications before buying them. Else, use the trial version.