I want to update my iPad version to get more apps

If your your ipad is telling you that you need to use an higher iPadOS version in order to run youtube, you should check settings>general>software update

If that screen is telling you “your iPad is up to date” with an old version of iPadOS your ipad is too old to run later iPadOS versions

It is a little hard to help/advise you when you provide little to NO useful information about your iPad.

Here are my questions to you.

Can you, please, confirm what year and model iPad do you have/own?

The “A” model number can be found on the aluminium back of your iPad, in very small print, right under the larger bold print “iPad” on the back of the iPad.

AND/OR

Supply the “M” model number, which can be found in the Settings app, under the General settings panel, then tap About.

What iOS/iPadOS version is this iPad, currently, running?

What is the rated, internal data storage space/capacity of your iPad model and how much of this free, internal data storage capacity is left inside of your iPad model?

All of that additional info can, also, be found in the Settings app, General settings panel, About.

Please try to make an attempt to answer all questions asked.

Thank You.

YouTube

What about YouTube?

You'll get a better chance to get your question answered if you start your own individual post instead of interrupting someone else's post question.