HOW LONG SHOULD CHARGE LAST IN IPAD PRO

It depends on how intensive what you streamed was. If you want to see what used your battery today, go to Settings > Battery and what used power today will be displayed. You may find that something was running in the background, or location services was running all day. There are loads of things which can eat up power. Once you determine what used power, make adjustments as appropriate.

If your iPad's screen is at near or full brightness all you can expect is maybe between 4-5 hours, or so, of battery power.

My older iPad gets between 7-8 hours of use doing a variety of tasks.

But when it comes to streaming any video content, all I get is over 5 hours, or so, of battery power with my screen at a little over 50% brightness.

Apple's battery claims are “up to” 9 hours, depending on various usages AND ONLY with screen auto brightness toggled to OFF and your iPad's screen manually set to 50% brightness.

Depending on your regular iPad usages, you may not get to that 9 hour limit or even close.

Streaming for 3 hours, will eat up a battery pretty fast, so based on that and not knowing what else you may have done with your iPad today (read email, text, etc), it wouldn't be unusual. If you know you're going to do something which is battery intensive, plug the iPad in and use it plugged in.