Using iMac late 2013 model as external monitor to MacBookPro Retina Mid 2015 model.

I have iMac 21.5 inch, late 2013 with Mojave OS. I also have MacBook Pro (Retina, 15-inch, Mid 2015) with Catalina OS. would it be possible for me to use my iMac as an external monitor for my MacBook Pro? if so, what cables do I need? Or what changes do I need to make to be able to use that iMac as external monitor?