U can't get a definite number for MOSFET's coz each block in PLL may be designed using different topologies, for example for a ring based VCO u have larger number of transistors than the LC based one, same for the charge pump and dividers and ...
But why u want to know the number of transistors ??
i think you should see some basic PLL blocks so you can assume the transistor no.
which i think is not a good way to detect the level complexity of a circuit .
as en example the digital circuits may conatins large no of transistors while it is not complex at all.
so donot depend on such a way and try to analyze each circuit to discover it .