This module is not a freestanding design, it needs the MIXCONSOLE to work and attaches to it via a special flat cable at the back.
The great thing is that you can chain as many of the 3CH modules as you like so could make a 28 channel mixer if you wanted!
(28 is the maximum number because all these modules have to be situated directly next to each other and on the widest available case you can only fit 8x 3CH and one MIXCONSOLE module in one row.)
https://wiki.aemodular.com/pmwiki.php/AeManual/MIXCONSOLE3CH
These merchants probably sell this module. Huh?
Tangible Waves MIXCONSOLE/3CH
Tangible Waves Tangible AE Modular