Can you use the web version? If that doesn't work then I suspect you are out of luck.
@funkiejack says he has an iPad 4 - that does support up to iOS 10.3. But sorry you cannot go higher than 9.3. If this is a deal-breaker, you may wish to trade-in your iPad 3 to a second-hand reseller and get an iPad that supports an iOS compatible with Teams. If you definitely need Teams, then this may not cost you very much.