can i run 70 LED (3 volts) on two 4V and 1.2AH batteries ?
First of all, connecting all of them in parallel is a bad idea. If you were to use ordinary (incandescent) lightbulbs, connecting them in parallel would be a good idea, but not when working with LEDs. When driving LEDs, you should care more about the current intensity that flows through them, and not so much about the voltage across them. The voltage should be able to vary in order to maintain the desired current.

This being said, with a parallel connection, you force the LEDs to have the same voltage across them while having no control over the current that each one draws. Small differences in the LEDs will cause some to draw more current than others, especially if you have LEDs of different colors.

For similar reasons, connecting batteries in parallel is not a good idea because you would waste energy by forcing them to have the same voltage. The one with higher voltage will try to charge the other, which is not desired and is a waste of energy.

Now the solution : 
I would make a mixed network of (35) groups of 2 LEDs connected in series. The groups should have a series resistor to limit the current. You then connect the 35 groups in parallel. This would both compensate for differences in LEDs and work with your batteries connected in series. 

A similar example can be seen here : 
http://girr.org/girr/tips/tips7/superbright_led_strip_schematic.jpg