How do you estimate the number of servers serving a single queue?
I know that on average a job should take j seconds to complete and jobs arrive under some poisson distribution. I also know on average how long a job takes including time in the queue k seconds.
If you assume Markovian service times as well as a Poisson arrival process, you have an M/M/c system (where c is the number of servers. See the corresponding Wikipedia page. You can get a point estimate of the number of servers from the standard formulas. There's no guarantee that the point estimate is an integer, so you may need to massage it a little, but it should be in the ballpark.