You need roughly 38 kVA unit. (Something like this: http://www.tuncmatik.com/?page=/en/urunler/id/227/eaton-9390-ups-40-160-kva.html
. Please note this is an example. It may not match your voltage requirement.)
Calculation is like this: 3 amp x 120 volt = 360 VA.
You have 74 machines. 360 VA x 74 ea. = 26640 VA. This should be corrected for efficiency and power factor.
26640 VA should be taken as 38000 VA, which is 38 kVA including eff and pf.
You should check it with an electrician in your country, of course.