you need to know the specs of your 3G dongle (which frequency bands it uses), then go into your tablets settings and rite under Data usage tap on the "More" Tab and look for the 3G support information and tap , there is the information on which frequency bands the tablet uses.......i am assuming you are running ICS......?
if your dongle is not compatible with your tablet you can always consider a WiFi hotspot device to use with your dongle to create your own WiFi connection to use on the go.
Iview 760, C.T. cm9 (9/13/12) - 4.0.4
Ampe A90, stock 4.0.3
H.P. Touchpad, 1.5Ghz, dual core & dual-boot OS, web OS 3.0.5 - cm9 tenderloin (nightly 4/29/13) - 4.0.4
Acer A210 - 4.1.1