Sidecar and ipad2 or 3

You haven't been clear on what Ipad you have, a model number would be able to confirm this. You haven't confirmed the age of the MacBook either, but below is the info on sidecar and what it requires, I would say no, but we can clarify when you provide what Ipad/MacBook you have

Have a look at this - Use your iPad as a second display for your Mac with Sidecar – Apple Support

Sidecar system requirements

Sidecar requires a compatible Mac using macOS Catalina and a compatible iPad using iPadOS 13:

Mac using macOS Catalina

• MacBook Pro introduced in 2016 or later
• MacBook introduced in 2016 or later
• MacBook Air introduced in 2018 or later
• iMac introduced in 2017 or later, plus iMac (Retina 5K, 27-inch, Late 2015)
• iMac Pro
• Mac mini introduced in 2018 or later
• Mac Pro introduced in 2019
•   

iPad using iPadOS 13

• iPad Pro: all models
• iPad (6th generation) or later
• iPad mini (5th generation)
• iPad Air (3rd generation)

If you have an old 2011, over 9-year old iPad and an over 8-year old, 2012 iPad 3, none of these iPads can upgrade beyond iOS 9.3.5/9.3.6.

They CANJOT upgrade and run iPadOS 13 or the new Apple SideCar feature.

These iPads are too old, too underpowered and completely incompatible with any newer version of iOS.

is what it is, today, in the year 2020!

Apple supports new iPad models for up to 5-6 years with third party app developers supporting these iPads for another 2-3 years after.

So, that is a total of between 7-9 years of iPad/iOS support!

Older iPad models, like the iPad 2, 3, 4 and 1st gen iPad Mini have ALL reached this support limit!

If you need an iPad that can run the latest and greatest versions of iOS, as well as, the most current apps available, then, you need to purchase a new iPad from Apple or a discounted, refurbished iPad from Apple’s Refurbished & Clearance section of Apple’s Website or a new or refurbished iPad from an Apple authorised, third party retail or online reseller OR other trusted sources for new or used Apple products.

These old iPad 2, 3, 4 and 1st gen iPad Mini models are nearing 8 and 9-years old, now.

As of the beginning of 2019, many, MANY third party app developers are all more quickly and completely permanently dropping older app support for all old 7, 8 and 9-year iPads that are running 2-3 year old and earlier iOS versions ( iOS 10 and earlier ).

Third party app developers are removing all of their older, legacy versions of their apps from Apple's App Store servers, now.

Third party app developers no longer want to support these 8 and 9-year old or older iOS devices, any longer!

Older versions of apps are, soon, going to be gone for good, now!

Getting older versions of apps for these old iPad models, initially from Apple’s iOS App Store is getting very difficult and very problematic and this issue is getting, painfully, much worse in 2020, now!

These old iPads are now reaching their complete end of life and support.

So finding older versions apps for older iPads, while still possible, currently, will be a tough challenge, now, in 2020.

Old iPads that can no longer be upgraded/updated will have NO MORE APPS AVAILABLE for initial download, at all, soon, from the Apple iOS App Store, for such old iOS devices in the very near future.

Older versions of apps for these older iPads will be completely gone, at some point, in the very foreseeable future.

Again, it is what it is, today, in the year 2020!

So, this is really now the time to seriously consider a new or discounted, refurbished iPad from Apple or other Apple authorised resellers.

A lot has happened with iPad and iOS in 7-9 years and in the past 2 to 3-1/2 years since iOS 9 and 10.

As an example and compared to your older 8 and 9-year old iPad models,

The cheapest, baseline 2019, 10.2 inch screen 7th gen Apple iPads have a 1/2 inch larger retina screen, newer, more powerful and nearly 2-1/2 times faster 2.3 Ghz, A10 Fusion processors, AT LEAST, 3-4 times the internal RAM, with the 2019, 7th gen iPad having 3 GBs of internal RAM, iPadOS 13 support, with much better and improved multitasking features, Apple Pencil and Apple Smart keyboard cover support and have better audio speakers and better/improved built-in cameras.

In addition, if you search online and look at various, reputable online Apple device resellers, you can usually find this 2019, 7th gen iPad at discounts of between $60 U.S.D and $100 U.S.D. depending on storage size and whether it is a WiFi ONLY model or a WiFi/cellular data model.

Sorry & Best of Luck to You!

See the system requirements here for the use of Sidecar. Use your iPad as a second display for your Mac with Sidecar - Apple Support