Hi there!
If you have installed the Office 2016 before then you might have redeemed the license already on your Microsoft account. You just need to login using the correct account where you purchased or redeemed the Office 2016 to get the installer of it.
You can go to: https://account.microsoft.com/services
- Sign in with the same Microsoft account used before.
- Look for Office 2016 Standard in your services list.
- Click Install.
Now if you have the product key and haven't redeemed it yet. You can do so by going to https://office.com/setup
More details are available on the Microsoft support page: https://support.microsoft.com/en-us/office/download-and-install-or-reinstall-office-2021-office-2019-or-office-2016-7c695b06-6d1a-4917-809c-98ce43f86479
Please note that this is a public forum, I will be responding you in short period of time and regret for a delay in response. As I am merely a fellow user trying to provide insight and information that may be helpful to others. Thanks!