Hello Tiffany
Hi, I'm Karl, an independent advisor and will try to help you with this.
Office 2016 (or any individual '2016 app i.e. Outlook) is no longer available via the Microsoft Store.
You would have to find a reseller that still sells older versions of Office or individual apps. The one word of caution that I would give is to be wary of any online sites that offer Microsoft products at prices that are "too good to be true" since in 99.999% of those cases, it's because those prices are.
Before replying, I did check the BestBuy site and only found that "marketplace" resellers were offering older versions of Office or standalone apps - BestBuy only offered '2019 & '365. Also found Outlook '2016 offered on Amazon but to be honest, would personally be leary since what I did find wasn't being sold by Amazon itself but through one of the resellers.