You could do this in TM, but you'll have multiple AD/DA conversions happening per device, plus the inherent latency each conversion would add (would have to manually account for differing delays depending on the specific patch: 1 unit, 2 units, or all 3 units, and then playing from a live input via TM or being fed from a pre-recorded track off the DAW).  Certainly possible if you eat up 3 AD outs and 3 DA ins to connect the 3 units, and route in TM (and/or your DAW software) accordingly - but would seem to be a nightmare to get sample-accurate if that matters in your application (parallel processing, multi-mic setups, etc).

Cabling - 6x 1/4" TRS to TRS cables would work just fine to patch each unit's I/O to your UFX's rear line I/O's.

You would be a lot better off with a Patchbay to accomplish this patching task IMO - but with only 3 units, a patchbay is a bit overkill.  I'm also just jumping into a 96pt patchbay, and they ain't cheap At ALL!   I'd probably ponder manual patching for the time being - I did it for years and years with a much larger setup before it became a serious hindrance (thus my investment in a Patchbay).