Mirroring from iMac to MacBook Pro

Hello,

I am trying to mirror my Macbook Pro ( Mojave, 13 inch, 2016 two Thunderbolt ports) to my iMac (Mojave, Retina 4K, 21.5 inch, late 2015).

I was advised by an agent to purchase the following accessories in order to mirror the Macbook.

1. https://www.apple.com/shop/product/MD861LL/A/apple-thunderbolt-cable-20-m
2. https://www.apple.com/shop/product/MMEL2AM/A/thunderbolt-3-usb-c-to-thunderbolt-2-adapter

I am not sure if I was advised correctly, because I was not able to be present to show the agent my devices. Please advise on whether I was advised correctly, and if not, what I would need to do differently. Thanks!