How would you find the Blinding factor R in RSA blind signature algorithm? How would you find the Blinding factor $R$ in RSA blind signature algorithm when having – for example – $p=11$, $q=3$, message $m=6$, and public key $pk=7$?

The answer doesn’t have to use the numbers in the example. I’m just trying to understand how to find the blinding factor $R$ having any numbers.
You don't “find” the blinding factor. It is picked randomly before starting the computation. The whole point of blinding is to use a random value in the computation and to perform the computation in such a way that this random value affects intermediate values but not the final result.