I purchased a smart keyboard 4 years ago the same time I purchased a 12.9 ipad . Will that smart keyboard work with the Ipad Pro 2020 version?

I believe this is the one you have - https://www.apple.com/shop/product/MNKT2B/A/smart-keyboard-for-129%E2%80%91inch-ipad-pro-british-english?fnode=eebfc8c274902f20608520b110e09c513acfec46bce41cc3e15628267566082b271b6d4402d60d288098e8fb636b8d2ea40bd6ee1ec52ff1fa23a203e553cf89459dca0b11218aa407d0c1ab7b1715e988b73ab69510b0b5935cc3746d67756ec6e9281acaff0be79b0bf37fa28df8f5&fs=f%3Dipadpro_12_9_2%26fh%3D35d5%252B48e4

The above Smart Keyboard only works with the following ipads

• iPad Pro 12.9-inch (2nd generation)
• iPad Pro 12.9-inch (1st generation)

Short answer? No.

Nope, I believe they are different sizes and have changed shape

Hey there! Thanks for contacting the Apple Community, I'm here to help you out today!

If your smart keyboard uses bluetooth, your iPad should be able to connect to it. However, if your smart keyboard is not bluetooth-based, you may want to visit this link and scroll to find "Compatibility" : https://www.apple.com/shop/product/MNKT2D/A/smart-keyboard-for-129%E2%80%91inch-ipad-pro-german?fnode=1dcecd519ba0f9670a3dccc6e7898b5255e0a2a64aa04b865e650f01235a8ecc611816e716fcb3111b34288b95caa5019c42d2e5065d78f89f9f361f1aa230185014c89d9018d6e4e5ed170dd0a65bd8b44c5b6bea913e564b01707a26d8bef56617dcccb07aa06d1b874e7a4791bddf&fs=f%3Dipadpro_12_9_2%26fh%3D35d5%252B48e4&rdt=redirectionFromProductPage

If it is indeed that smart keyboard, it is compatible with the following iPad Models:

• iPad Pro 12.9-inch (2nd generation)
• iPad Pro 12.9-inch (1st generation)

I hope this helps!