My 3rd generation iPad lags a lot. How to do a factory reset?

Hello,

Please refer to the following Apple Support document.

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

It is worth mentioning that iPad (3rd generation)’s support ended 6 years ago which means you would be unable to download most applications from the App Store. You may be better off just resetting iPad’s settings and not doing a complete restore.

Settings > General > Reset > Reset All Settings

Be certain you do not select Erase All Content and Settings as this will erase all of your information. It is a good idea to perform a backup of your iPad prior to resetting its settings.

Tap on the link below to my iDevice/iOS performance/optimisation user tips link.

Slow iPad on iOS 9, 10 or 11! - Apple Community

Try all of these tips and leave each tip active together.

Do NOT simply try every tip individually, expecting just one tip to be a performance “cure all”.

Many of these tips are designed to work together to help improve overall iOS/iDevice performance.

Good Luck!

Also, how much internal, free data storage space is left inside of your iPad.