Office for iPhone

If you add your Outlook mail to the Mail app, you will not receive any advertisements

See this Apple article:  Add an email account to your iPhone, iPad or iPod touch

Add an email account to your iPhone, iPad or iPod touch – Apple Support (UK)

At this point I believe all you can get is Office 365. Also, if you do not have an Office 365 account, you can no longer create or edit files. I had gotten the apps individually, i.e. Word, Excel, etc. and then it got to where you could not do anything except view files in the apps. They require the Office 365 account. That is how Microsoft has configured their apps now.

Open the App Store and search for “MS Office"

Check here -> https://apps.apple.com/us/app/microsoft-office/id541164041

This one is not a Microsoft 365, see -> https://apps.apple.com/us/app/officesuite-docs-pdf-editor/id924005506