The naming convention used in Sawtooth Software is locked in (standard).
You can write the existing variables Q3_1, Q3_2, Q3_3 to new variables Q3a,Q3b,Q3c using the SetValue function as follows ...
You can place these scripts in to the footer of any question, but ensure you place them after Q3 has been answered. You will also need to define Q3a,Q3b,Q3c as new variables in the pass-in fields section.
So instead of exporting Q3_1, Q3_2, Q3_3, you can now export Q3a,Q3b,Q3c.
As alternative you can export from Lighthouse Studio and rename variables in the other software (e.g. SPSS, Excel, etc.).