@Jacky_R and @SandyWy
There should be no problem for a meeting you've already scheduled and sent out links for after you upgrade your account. Just be sure that the licenses (Pro license and Large meeting add-on) are assigned to the host of that meeting before you start the meeting.
In general, Zoom checks the license of the meeting host when the meeting is started, not when it's scheduled. Thus, if it was scheduled as a Basic account, but started as a Pro account, Zoom will allow access to all Pro features. Same thing for the add-on. If you start the meeting as a standard Pro user, you can have up to 100 participants, but if you start the meeting with a Large meeting add-on assigned to you, your attendance capacity will go up to the max associated with that add-on.
If this has answered or help find a solution to your question , please click the Accept as Solution button below so that others in the Community may benefit as well.
Cheers!