Is this a tidy up exercise?
The plate you show works on the format of all main feeds for aerial and sat going in to a amp, from the amp you have a feeder cable to each of any number of locations and there you use the plate type you've shown.
If you only have one back box for the three cables you have then it needs to be quite deep (35mm+), buy a single blank flat plate and drill three holes in it.
You buy mountable f type to f type and tv aerial barrels and set them in to the blanking plate. A dab of decent glue (a glue gun is ok, sticks like poo works).
You then make off the three cables and fit them on the inside and close the plate.
Personally I'd suggest
Frames in white, black, metal..