Calculating a probability that a random number will be between two numbers from a data set

So, I have generated a random, normally distributed population of data that has a mean of 341.08 and a standard deviation of 3.07. Here's that code:

pop<-rnorm(1000, mean=341.08,sd=3.07)

Now, I need to find out the probability that a random number picked will fall between 337 and 343 (both numbers included). How would I execute this?