IF each bulb is identical then the 9V is split evenly with 3V across each of 3 bulbs.
Also remember that Ground is an optional symbol to represent 0V ( not necessarily earth ground) at any point for voltage references and current flows from V+ towards lower voltages. Other nodes may be 0V too if there is 0 resistance or 0 current between them since the product is (\$\Delta V=IR\$) which means the voltage drop. But that is not relevant here as we expect current to flow in a loop shown in your schematic.
For KVL and KCL simple rules of calculation and also intuitive flow of current from a battery or any Voltage source, we use the convention for +current to flow from the +ve source and towards the -ve voltage.
Remember this is a LOGIC DIAGRAM or schematic and not a molecular physics diagram, so we EE's use this logic to speed up analysis with intuition. ( as some famous person once said, "it's all relative")
We don't think about how actual electrons collide with each other like a lineup Queue where one person bumps into the next and travels at the speed of light for a given dielectric surrounding the conductor with electrons (-) attracted towards the positive (+) conductor terminal between resistor with a shared current flow I=dQ/dt of charges.
... unless we want to examine molecular physics of static charges along with an AC or DC excitation that contribute to voltage breakdown before the actual breakdown arc (negative resistance) occurs. I only do this for failure analysis on double electric charge capacitors (Supercaps) , same as batteries and UHV transformer insulation failures (e.g.>20kV) but not for electronics per se.