Soviets didn't have Yak-3P operational during WWII or in any other wars for that matter.
according to Erik Pilawskii Yak3p saw action in Manchuria:
quote "The final VK-105-engined variant was the fearsome Yak-3P (pushechniy, or cannon), armed with three of the new 20mm B-20 lightweight cannons, each with 130 rounds of ammunition.
Unfortunately, the type just missed the end of hostilities in Europe, though two squadrons were operational against the Japanese from 8 August. These were untouchable and the Yak-3P was said, when attacking, to cut even modern and protected Japanese aircraft (such as the Ki-84 and Ki-61) in half like a buzz saw".