My mistake, I forgot that you wanted to go to 34t. Indeed, for 34t, you need a BCD 110 crankset or any of the latest 4 arms crankset.

I never dismounted the crankset of my Birdy 3, I do not know the diameter of its axle.

But the bottom bracket box is standard, so if you also change the external bearings, you can mount any crankset with an integrated axle with its matching external bearings or if you prefer a classic bottom bracket, any standard square taper (but I wouldn't do that) or Isis bottom bracket + crankset..