How to get the electric power in each resistor when there's only one voltage in a circuit?
OK, hard to give a full answer without knowing the values of V and all resistor(s) or the circuit configuration, but I’ll give a theory-based answer.
The voltage dropped across each resistor depends on how they are arranged: in series the potential difference (p.d. or voltage) across each resistor is in proportion to that resistance. [e.g. for a p.d. of 6V two resistors of size 4
Once you know the p.d. across each individual resistance you can find the power dissipated from