We can store all the primes up to $l$ in a list. The list, however, will be impractical.
Question is: given $n$ find the $n-th$ prime.
The interesting part, actually, we don't need to find exactly $n-th$ prime. Finding a unique prime for each $i, 1 \leq i \leq n$ is enough.
Mathematica can find the $n$th prime extremely quickly. For instance, it can find the $10^{10}$th prime ($252097800623$) in $0.55$ seconds.