Here's my attempt...
Thank you for the reply, I've been thinking about this problem for the past few days and I think it's saying that you have this given solution (1mM), but given the limitation that you can only take out 1 micro liter, what concentration does it need to be in order to end up with a 5nM solution with a volume of 1 mL. This means that v1 is set to your limitation (1 microliter) since you have to remove that amount and dilute it to 1mL. This means c1 is unknown and can't be 1mM since you are trying to find out what you need to dilute the 1mM solution to in order to get a 5nM solution with a volume of 1 mL.
Since c2 and v2 are both known as they're the values you want to end up with, I believe this is the way to solve this problem:
v1c1=v2c2
(1microliter)c1=(1ml)(5nM)
(1microliter)c1=(1000microliters)(5nM)
c1= 5000nM
So, you need to dilute the 1mM stock solution to 5000nM, then take 1microliter of that and dilute to 1mL to have a solution with a concentration of 5 nM.
If you or anyone can double check me on this logic, I'd really appreciate it.