What is the distance between Jupiter and the L4 and L5 points of the Sun-Jupiter system? I need it to attempt to calculate the $\Delta v$ needed to reach Jupiter from there.
L4 and L5 are the same distance from Jupiter as Jupiter is from the sun: about 5.2 A.U. L4, the sun and Jupiter form an equilateral triangle. Ditto L5, sun, Jupiter. All together, L4, Jupiter, L5, sun form a 120º/60º rhombus.
As Mark Adler says, distance and delta V are different things.
Describe your scenario in more detail and I might be able to help with the delta V. Are you thinking of going from a Trojan asteroid to one of Galilean moons? What trip time do you have in mind?
According to this, L4 and L5 for Sun-Jupiter will each be at the same distance from Jupiter as Jupiter is from the Sun (something like 780,000,000 km).