MS Office doesn’t exist for iPad per-se. However, you will find many of the individual MS Apps (Word, Excel, Outlook, OneNote etc.) in the App Store - for which you will need an active Office 365 Subscription.
Basic functionality is available for free for screen sizes 10.1” and less; for any devices with a screen larger than 10.1”, functionality is limited to open/review only. Full functionality required an O363 Subscription.
There is MS Office product for iPhone - not iPad - that is a very cut-down (single install) office suite App.
If you need to purchase an O365 Subscription, it often cheaper and more flexible to purchase the sub’ directly from Microsoft. You’d be well advised to compare prices before purchase.
I hope this information and clarification is helpful.