Am I able to call 911 from an ipad that is connected to wifi?

You cannot call any number from any iPad! An iPad is not a cellular telephone. That is true regardless of whether it is a cellular model iPad or not.

If you happen to have an iPhone, then the iPad can use the iPhone to make calls using Handoff. In this case, any iPad could be used when connected to Wi-Fi.

If you have a VOIP telephone app like FaceTime, Skype, etc. yes. But you need some form of internet telephone app and service to make any kind of phone call at all from an iPad.

If you have an iPhone set to share calls with that iPad, then it can make cellular telephone calls (actually, the iPhone makes or receives the call, but it shares it with the linked iPad or Mac using an iOS and macOS feature called continuity).

If your iPhone carrier offers WiFi calling and sharing WiFi calling between devices, that’s another way a device other than a cell phone can call 911.

But be aware that any 911 call over the internet may have no location info or only very approximate location info, so you will have to describe where you are. Also check if your local 911 call center uses texts yet - some, but not many yet, do take 911 texts.