Can I use this thunderbolt 3 pro cable to connect iMac with another iMac?

You can set up target disk mode with the thunderbolt cable:

Transfer files between two Mac computers using target disk mode - Apple Support

AppleFan3421 wrote:

It is possible to use the other mac as a second display. ...

Absolutely wrong! 2014 and later iMacs do not support Target Display Mode.

It is possible to use the other mac as a second display. But if you are trying to launch a cable connection to send files, what’s the point when AirDrop exists? If you are trying to get more computing power, it doesn’t work, while giving more load to the first mac.

dennyLu wrote:

All the Macs has thunderbolt 3 ports now. Is it possible to use thunderbolt 3 pro cable to connect Macs?

And do what?