Are you talking about Lightroom Classic? Perhaps via the Adobe Photography plan?
That is not normally obtained via the Microsoft Store. It is obtained from Adobe. To cancel a Adobe plan, a subscription, generally involves bringing up Adobe.com in your Internet Browser, Signing in (probably same account you used to get into this community) and managing your plan.
For my curiosity I went to the Microsoft Store. No Lightroom Classic shown. Now Lightroom is shown, that is the cloud based version. And when I look at it, it is a trial version, and it is stated a Adobe Subscription is required to use it after the trial.
Note that Adobe has a contract with you for a years use of the subscription, even if you pay monthly. So typically you are on the hook for the entire 12 months, their may be a option to cancel, and not continue with paying the monthly, but with a penalty cost. If you pay annually, I have n clue if they might rebate, I doubt that.
As stated, not Adobe, so take with a grain of salt.